CBSE Class 10 Science Chapter 12 Electricity Very Short Answer Questions

CBSE Class 10 Science Chapter 12 Electricity Very Short Answer Questions

Question 1. In an electric circuit, state the relationship between the direction of conventional current and the direction of flow of electrons.
Answer: The direction of conventional current is opposite to the direction of the flow of electrons.

Question 2. Write a relation between heat energyproducedin a conductor when a potential difference Vis applied across its terminals and a current flows through for
Answer: Heat produced, H = Vlt.

Question 3. How will the resistivity of a conductor change when its length is tripled by stretching it?
Answer: The resistivity of a metallic conductor does not depend on the length of the wire, so it will remain the same.

Question 4. Why is a series arrangement not used for connecting domestic electrical appliances in a circuit?
Answer: If anyone stops working due to some reason, others will also stop working.

Read and Learn More CBSE Class 10 Science Very Short Answer Questions

Question 5. The radius of the conducting wire is doubled. What will be the ratio of its new specific resistance to the old one?
Answer: 1: 1, as it depends on the nature of the material only.

CBSE Class 10 Science Chapter 12 Electricty.

Question 6. State which has a higher resistance—a 50 W or a 25 Wlamp bulb and how many times?
Answer: We know that \(\mathrm{R}=\frac{\mathrm{V}^2}{\mathrm{P}} \quad \text { or } \quad \mathrm{R} \propto \frac{1}{\mathrm{P}}\)

Thus, a 25 W lamp has double the resistance of a 50 W lamp.

Question 7. A bulb gets dimmer for a moment when a geyser connected across the same source is
switched on. Why?
Answer: The geyser draws a heavy current for a moment which causes a potential dropin the line. Due to this, the bulb gets dimmer.

Question 8. Why is an ammeter likely to burn, if you connect it in parallel?
Answer: If an ammeter is connected in parallel, the resultant resistance of the circuit decreases and more current passes through the instrument. Hence, the ammeter is likely to burn out.

Question 9. What happens to the resistance of a conductor when temperature is increased?
Answer: Its resistance increases.

Question 10. What is the resistance of an electric arc lamp, if the lamp uses 20 A when connected to a 220-volt line?
Answer: \(\mathrm{R}=\frac{\mathrm{V}}{\mathrm{I}}=\frac{220}{20}=11 \mathrm{ohm}\)

Question 11. Define one watt.
Answer: The power expended by a source through it under a potential difference of 1 volt.

Question 12. The power of a lamp is 60 W. Find the energy in joules consumed by it in Is. 
Answer: Energy consumed = P x t

=60×1

=60

Question 13. State a difference between the wire used in the element ofan electric heater and in a fuse wire.
Answer: The wire used in the element ofan electric heater has a very high resistance while that in a fuse wire has a low resistance.

Question 14. In an electric circuit, state the relationship between the direction of conventional current and the direction of flow of electrons.
Answer: The direction of conventional current is opposite to the direction of the flow of electrons.

Question 15. Calculate the number of electrons constituting one coulomb of charge
Answer: Number of electrons = \(\frac{1 \mathrm{C}}{1.6 \times 10^{-19} \mathrm{C}}\)

= 0.625×1019

=6.25×1018

CBSE Class 10 Science Chapter 12 Electricity

Question 16. A wire resistivity ‘p’ is pulled to double its length. What will be its new resistivity?
Answer: Resistivity remains the same i.e., ‘p’.

Question 17. Why is heat produced when a current is passed through a conductor?
Answer: During their motion, the electrons collide with one another and hence lose some kinetic energy. This loss of kinetic energy is dissipated as heat across the conductor.

Question 18. Why is tungsten metal selected for making filaments of incandescent lamps?
Answer: It is because tungsten has a high melting point.

Question 19. What will happen to the current in a circuit, if the fit resistance is doubled?
Answer: The current becomes half.

Question 20. Give two applications of the heating effect of current.
Answer: Electric Geyser and Electric Iron.

Question 21. What is meant by 1-ohm resistance?
Answer: The resistance of the conductor is said to be 1 ohm ifundor a potential difference of 1 volt a current of one ampere flows through the conductor.

Question 22. What is the resistance ofan ideal ammeter?
Answer: An ideal ammeter has zero resistance.

Question 23. Why is much less heat generated in long electric cables than in filaments of electric bulbs?
Answer: It is because the resistance of the filament of an electric bulb is much more than that of an electric cable.

Question 24. A resistance of 1 kg has a current of 0.25 A throughout it when it is connected to the terminal of a battery. What is the potential difference across the ends of a resistor?
Answer: From Ohm’s law,

V = IR = 0.25 x 1000 = 250 V.

Question 25. Why is manganin used for making standard resistors?
Answer: Mangan being an alloy has a low temperature coefficient of resistance.

Question 26. How is an ammeter connected in a circuit to measure current flowing through it?
Answer: It is always connected in series in a circuit through which the current is to be measured.

Question 27. 400 J of heat is produced in 4s in a 4 Q. resistor. Find potential differences across the resistor.

Answer: \(\begin{aligned}
& \mathrm{H}=\frac{\mathrm{V}^2 t}{\mathrm{R}} \\
& \mathrm{V}=\sqrt{\frac{\mathrm{RH}}{t}}=\sqrt{\frac{4 \times 400}{4}}=20 \mathrm{~V}
\end{aligned}\)

Question 28. Give one example of metal which is the best conductor ofheat.
Answer: Silver or Copper

Question 29. A given length of wire is doubled on itself and this process is repeated once again. By what factor does the resistance ofthe wire change?
Answer: Length \(\frac{\mathrm{L}}{4}\) and area 4 times

⇒ \(\mathrm{R}=-\frac{e \frac{\mathrm{L}}{4}}{4 \mathrm{~A}}=\frac{e \mathrm{~L}}{\mathrm{~A}} \times \frac{\alpha 1}{16}=\frac{1}{16} \times \frac{e \mathrm{~L}}{\mathrm{~A}}\)

Hence, the resistance changes by \(\frac{1}{16}\)

Question 30. Why do we use copper and aluminum wire for the transmission of electric current?
Answer: They have low resistivity and are good conductors of heat.

Question 31. What does an electric circuit mean?
Answer: An electric circuit is a continuous and closed path along which an electric current flows.

Question 32. Define the unit of current.
Answer: If one coulomb of charge flows through any conductor section in one second, then the current through it is said to be one ampere. 1A=1Cs-1

Question 33. Name a device that helps to maintain a potential difference across a conductor.
Answer: A battery

Question 34. What is meant by saying that a potential difference between two points is 1V?
Answer: The potential difference between two points is 1 volt if one joule of work moves a positive charge of one coulomb from one point to the other.

Question 35. How much energy is given to each coulomb of charge passing through a 6 V battery?
Answer: Energy given by battery

Charge x Potential difference

= 1C x 6 V

= 6

Question 36. Calculate the number of electrons constituting one coulomb of charge.
Answer:

Charge on one electron, e=1.6×10-19c

Total charge, Q=1Cs

Number of electrons, \(n=\frac{q}{e}\)

⇒ \(n=\frac{1 \mathrm{C}}{1.6 \times 10^{-19} \mathrm{C}}\)

n = 6.25 x 1018.

CBSE Notes For Class 11 Chemistry For Heat of Reaction

Heat Of Reaction

Heat Of Reaction Definition

The amount of heat absorbed or evolved in a reaction when the stoichiometric number of moles of reactions indicated by the balanced chemical equation, is completely converted into products at given conditions is called the heat of reaction at that conditions.

At a particular temperature, the heat of a reaction depends on the conditions under which a reaction is occurring. Generally, chemical reactions are carried out either at constant pressure or at constant volume. Accordingly, the heat of reaction is of two types, namely Heat of reaction at constant volume and heat of reaction at constant pressure.

The heat of reaction at constant volume

The amount of heat absorbed or evolved in a reaction when the stoichiometric number of moles of reactants, indicated by the balanced chemical equation of the reaction, is completely converted into products at a fixed temperature and volume is called the heat of reaction at constant volume.

Explanation: Let us consider a chemical reaction that is occurring at constant temperature and volume.

⇒ \(a A+b B \rightarrow c C+d D\)

According to die first law of thermodynamics, if a reaction occurs at constant volume then the heat change (qv) is equal to the change in internal energy (AU) ofthe system (provided only pressure-volume work is performed), qv= ΔU

Therefore, for the reaction

⇒ \(q_V=\Delta U=\Sigma U_{\text {products }}-\Sigma U_{\text {reactants }}=\Sigma U_P-\Sigma U_R\)

where ΣUp = total internal energy of products and I UR = total internal energy of reactants.

∴ \(q_V=\Sigma U_p-\Sigma U_R=\left(c \bar{U}_C+d \bar{U}_D\right)-\left(a \bar{U}_A+b \bar{U}_B\right)\)

Where \(\bar{U}_A, \bar{U}_B, \bar{U}_C \text { and } \bar{U}_D\) die molar internal energies of A. B. Cand D, respectively. Thus, the heat of reaction for a reaction at constant temperature and volume is the difference between the total internal energy of tire products and the total internal energy of the reactants.

Example:

⇒  \(\mathrm{CH}_4(\mathrm{~g})+2 \mathrm{O}_2(\mathrm{~g}) \rightarrow \mathrm{CO}_2(\mathrm{~g})+2 \mathrm{H}_2 \mathrm{O}(\mathrm{l})\)

For the above reaction, the heat of the reaction at a constant volume:

⇒ \(q_V=\left[\bar{U}\left(\mathrm{CO}_2, g\right)+2 \bar{U}\left(\mathrm{H}_2 \mathrm{O}, l\right)\right]-\left[\bar{U}\left(\mathrm{CH}_4, g\right)+2 \bar{U}\left(\mathrm{O}_2, g\right)\right]\)

Where

⇒ \(\bar{U}\left(\mathrm{CO}_2, \mathrm{~g}\right), \bar{U}\left(\mathrm{H}_2 \mathrm{O}, l\right), \bar{U}\left(\mathrm{CH}_4, g\right) \text { and } \bar{U}\left(\mathrm{O}_2, g\right)\)

Are die molar internal energies of CO,(g), H2O(I), CH4(g) respectively.

Heat of reaction at constant pressure:

The amount of heat absorbed or evolved in a reaction when the stoichiometric number of moles of reactants, indicated by a balanced chemical equation of the reaction, is completely converted into products at constant pressure, and temperature is called the heat of reaction at constant pressure.

The heat of reaction at constant pressure Explanation:

Let us consider a reaction that is occurring at constant temperature and pressure: aA + bB →+ cC + dD. According to the first law of thermodynamics, if a reaction occurs at constant pressure, then the heat change in the reaction is equal to the change in enthalpy of the system (provided only pressure-volume work is performed). Thus, qp = ΔH. Therefore, for the reaction,

⇒ \(q_P=\Delta H=\Sigma H_{\text {products }}-\Sigma H_{\text {reactants }}=\Sigma H_P-\Sigma H_R \text { ; }\)

where Hp = total enthalpy ofthe products and HR = total enthalpy of the reactants

∴ \(q_P=\Sigma H_P-\Sigma H_R=\left(c \bar{H}_C+d \bar{H}_D\right)-\left(a \bar{H}_A+b \bar{H}_B\right)\)

where, \(\bar{H}_A, \bar{H}_B, \bar{H}_C \text { and } \bar{H}_D\) are the molar enthalpies of A, B, C, and D, respectively.

Thus, for a reaction, the heat of the reaction at constant temperature and pressure is equal to the difference between the total enthalpy of products and the total enthalpy of reactants.

Example:

For the Reaction, \(2 \mathrm{H}_2(\mathrm{~g})+\mathrm{O}_2(\mathrm{~g}) \rightarrow 2 \mathrm{H}_2 \mathrm{O}(l)\) the heat ofreaction at constant pressure is given by;

⇒ \(q_P=2 \bar{H}\left(\mathrm{H}_2 \mathrm{O}, l\right)-\left[2 \bar{H}\left(\mathrm{H}_2, \mathrm{~g}\right)+\bar{H}\left(\mathrm{O}_2, \mathrm{~g}\right)\right]\)

Where \(\bar{H}\left(\mathrm{H}_2 \mathrm{O}, l\right), \bar{H}\left(\mathrm{H}_2, \mathrm{~g}\right) \text { and } \bar{H}\left(\mathrm{O}_2, \mathrm{~g}\right)\) are the molar enthalpies of H2O(g) , H2(g) and O2(g) , respectively.

Relation between heat of reaction at constant volume [qv) and heat of reaction at constant pressure (qp)

If a reaction is carried out at a fixed pressure than the heat of the reaction, qp = change in enthalpy in the reaction, ΔH. …………………(1)

If the reaction is carried out at constant volume then the heat of the reaction, qv = change in internal energy in the reaction, ΔU …………………(2)

If the changes in internal energy and volume in a reaction occurring at constant pressure are AUp and AV, respectively, then according to the relation H = U + PV

⇒ \(\Delta H=\Delta U_P+\Delta(P V)=\Delta U_P+P \Delta V\)

[As pressure (P) is constant, Δ(PV) = PΔV

∴ \(q_P=\Delta H=\Delta U_P+P \Delta V\) …………………(3)

since qp = ΔH

Subtracting equation [2] from [3], we obtain

∴ \(q_P-q_V=\Delta U_P+P \Delta V-\Delta U=\left(\Delta U_P-\Delta U\right)+P \Delta V\)

At a particular temperature, the difference between AUp (change in internal energy at constant pressure) and AU (change in internal energy at constant volume) is very small. Therefore, it is considered that

⇒ \(\Delta U_P \approx \Delta U.\)

Since qp -qv = PΔV

Or, ΔH-ΔU = PΔV ………………………….(4)

In the case of solids and liquids:

For reactions involving only solids and liquids, the change in volume (ΔV) of the reaction system is negligibly small. So, in such reactions, the heat of the reaction at constant pressure (qp or ΔH) becomes equal to the heat of the reaction at constant volume (qV or ΔU).

In the case of gases:

For a reaction involving gaseous substances

Example:

⇒  \(A(g)+B(g) \rightarrow C(g) \text { or } A(g)+B(g) \rightarrow C(I)\),

Or \(A(s) \rightarrow B(s)+C(g)\), etc.]

The change in volume (Δ V) of the reaction system may be sufficiently high. We can determine the value of PΔV as illustrated below

Let us consider a gaseous reaction that occurs at constant pressure (P) and temperature (T).

Suppose, n1 and V1 are the total number of moles and the total volume of the reactant gases, respectively, and n2 and IA, are the Here, total number of moles and the total volume of the product gases respectively. If the gases are assumed to behave ideally, then for gaseous reactants PV1 = n1RT., and gaseous products PV2 = n2RT.

∴ \(P\left(V_2-V_1\right)=\left(n_2-n_1\right) R T \text { or, } P \Delta V=\Delta n R T\)

Substituting ΔnRT for PΔV into equation (4) we obtain

⇒  \(q_p-q_V=\Delta n R T \text { and } \Delta H-\Delta U=\Delta n R T\)

∴ \(\left[\boldsymbol{q}_p=\boldsymbol{q}_V+\Delta n \| T\right] \text { and }[\Delta I=\Delta U+\Delta n \ RT] \cdot \cdot \cdot \cdot \cdot [5]\)

Using equation (5), ΔH (or qp) can be calculated from the known value of U (or Δv), and ΔU (or qV) can be calculated from the known value of AII (or ΔyU). If

Δn=0; ΔH=ΔU;Δn>0,ΔH>ΔU;Δn>0,ΔH<ΔU.

Comparison between the values of ΔH and ΔU for gaseous reaction having different Δn values:

CBSE Class 11 Chemistry Notes For Chapter 6 Chemical Thermodynamics Comparison between the value

Standard State And Standard Reaction Enthalpy

Enthalpy change in a reaction depends on the conditions of temperature, pressure, and physical states of the reactants and products. To compare enthalpies of different reactions, we define a set of conditions called standard state, at which the values of AH for different reactions are calculated.

Standard State:

The standard state ofa substance is defined as the most stable and purest state of that substance at the temperature of interest and atm pressure. In the definition of the standard state, temperature is not specified like pressure (1 atm). If the temperature is not mentioned, then 25 °C (298.15 K) is taken as a reference temperature. However, this does not mean 25 °C is the standard temperature. A pure substance can have different standard states depending on the temperature of interest, but in each of these states, the pressure is always 1 atm.

Examples:

  • The standard state of liquid water at a particular temperature means H2O(l) at that temperature and 1 atm pressure.
  • The standard state of ice at a particular temperature means pure H2O(s) at that temperature and atm pressure.
  • The standard state of liquid ethanol at 25 °C means C2H5OH(l) at 25 °C and 1 atm pressure.

Standard enthalpy of reaction:

The standard enthalpy change of a reaction is defined as the enthalpy change that occurs when the stoichiometric number of moles of reactants, indicated by the balanced chemical equation of the reaction, is completely converted into products at a particular temperature and l atm (i.e., at the standard state).

The standard enthalpy of reaction at a particular temperature ( T K) is denoted by \(\Delta H_T^0\). The superscript ‘0’ indicates the standard state, and the subscript T indicates the temperature in the Kelvin scale.

Explanation:

⇒ \(\mathrm{C}_3 \mathrm{H}_8(\mathrm{~g})+5 \mathrm{O}_2(\mathrm{~g}) \rightarrow 3 \mathrm{CO}_2(\mathrm{~g})+4 \mathrm{H}_2 \mathrm{O}(l)\)

For this reaction \(\Delta H_{2 \mathrm{qg}}^0=-2220 \mathrm{~kJ}\) indicating that at.

  • 298 K temperature and atm pressure, if lmol of propane (C3H8) and mol of O2 react completely to form 3 mol of CO, and 4 mol of water at the same temperature and pressure (i.e, 29S K and atm respectively), then 2220 kj of heat will be evolved.
  • Alternatively, it can be said that at 298K temperature and 1 atm pressure, the change in enthalpy for the following reaction is =-2220 kJ.

CBSE Class 11 Chemistry Notes For Chapter 6 Chemical Thermodynamics Enthalphy

Factors affecting the reaction enthalpy

1. Physical states of reactants and products:

During the change of physical states of a substance (like solid, solid→ liquid, liquid→ vapor, etc.) heat is either absorbed or evolved. Thus, the value of the heat of the reaction or enthalpy of the reaction depends upon the physical states ofthe reactants and products. For example, in the following two reactions, due to the different physical states ofthe products,

The values ofthe heat of the reaction are different:

⇒ \(2 \mathrm{H}_2(g)+\mathrm{O}_2(g) \rightarrow 2 \mathrm{H}_2 \mathrm{O}(l) ; \Delta H=-571.6 \mathrm{~kJ}\)

⇒ \(2 \mathrm{H}_2(g)+\mathrm{O}_2(g) \rightarrow 2 \mathrm{H}_2 \mathrm{O}(g) ; \Delta H=-483.6 \mathrm{~kJ}\)

2. The condition under which the reaction is conducted:

At a particular temperature, a chemical reaction can be conducted either at constant pressure or at constant volume. If a reaction occurs at constant pressure, then the heat of reaction (qp)

⇒ \(=H_{\text {product }}-H_{\text {reactant }}=\Delta H\)

Occurs at constant volume, then the heat of reaction (qp) — The relation between ΔH and ΔH is ΔH = ΔH + PΔV The quantity PAV indicates pressure-volume work.

  • So, the difference between ΔH and AH is equal to the pressure-volume work involved during the reaction.
  • If the volume of the reacting system remains fixed (ΔV = 0), then pressure-volume work = 0 and ΔH = ΔH.
  • If the volume ofthe reacting system changes (ΔV=0), then, the pressure-volume work, PΔV≠0 and ΔH≠ΔU.

3. Allotropic forms of the reacting elements:

As the different allotropic forms have different enthalpies, the value of reaction enthalpy depends upon the allotropic forms of the reactants.

For example, the enthalpies of the reaction are different for the oxidation of graphite and diamond (two allotropic forms of carbon)

⇒ \(\mathrm{C}(\text { graphitè, } s)+\mathrm{O}_2(\mathrm{~g}) \rightarrow \mathrm{CO}_2(\mathrm{~g})\)

ΔH=-393.5 kJ

⇒\(\mathrm{C}(\text { diamond, } s)+\mathrm{O}_2(g) \rightarrow \mathrm{CO}_2(g)\)

Δ H =-395.4 kJ

4. Amount of the reactants:

As enthalpy is an extensive property, the magnitude of enthalpy change in a reaction (ΔH) is proportional to the amount of reactants undergoing the reaction.

For example, in the reactions given below, the magnitude of ΔH (reaction enthalpy) for reaction (1) is twice that for the reaction (1). This is because the total number of moles of reactants in the reaction (2) is twice as many as that in the reaction (1).

⇒ \(\mathrm{H}_2(g)+\frac{1}{2} \mathrm{O}_2(g) \rightarrow \mathrm{H}_2 \mathrm{O}(l), \Delta H=-285.8 \mathrm{~kJ}\) ……………………………..(1)

⇒ \(2 \mathrm{H}_2(g)+\mathrm{O}_2(g) \rightarrow 2 \mathrm{H}_2 \mathrm{O}(l), \Delta H=-571.6 \mathrm{~kJ}\) ……………………………..(2)

5. Temperature:

Temperature has a significant effect on the reaction enthalpy of a reaction. The extent of temperature dependence of the reaction enthalpy depends on the nature of the reaction.

Heat Of Reaction Numerical Examples

Question 1. The value of ΔH for the given reaction at 298K is — 282.85 kj. mol-1. Calculate the change in internal energy: \(\mathrm{CO}(g)+\frac{1}{2} \mathrm{O}_2(\mathrm{~g}) \rightarrow \mathrm{CO}_2(\mathrm{~g})\)
Answer:

We know, ΔH = ΔH + ΔnRT where, Δn = (total number of moles of the gaseous products) — (total number of moles of the gaseous reactants)

For the given reaction, ,\(\Delta n=1-\left(1+\frac{1}{2}\right)=-\frac{1}{2}\)

As per given data, ΔH = -282.85 kj-mol-1 & T = 298 K

∴ \(-282.85=\Delta U+\left[\left(-\frac{1}{2}\right) \times 8.314 \times 10^{-3} \times 298\right]\)

∴ \(\Delta U=-281.61 \mathrm{~kJ} \cdot \mathrm{mol}^{-1}\)

Question 2. The bond energy of a diatomic molecule IN given as the change in internal energy due to dissociation of that molecule. Calculate the bond energy of O2. Given: \(\mathrm{O}_2(\mathrm{~g}) \rightarrow 2 \mathrm{O}(\mathrm{g}) ; \Delta H=498.3 \mathrm{~kJ} \cdot \mathrm{mol}^{-1}, T=298 \mathrm{~K}\)
Answer:

In the dissociation reaction of O2 molecules, Δn = 2-1 = 1.

We know, ΔH = ΔU + ΔnRT

As given, ΔH = 498.3 kj.mol-1 , T = 298 K

∴ \(498.3=\Delta U+\left(1 \times 8.314 \times 10^{-3} \times 298\right)\)

or, ΔU= 495.8J

∴ Bond energy of O2 molecule = 495.8 kj.mol-1

Question 3. Calculate the values of ΔH and ΔH in the vaporization of 90 g of water at 100°C and 1 atm pressure. The latent heat of vaporization of water at the same temperature and pressure = 540 cal g-1.
Answer:

⇒ \(90 \mathrm{~g} \text { of water }=\frac{90}{18}=5 \mathrm{~mol} \text { of water. }\)

Vaporisation of water:

⇒ \(\mathrm{H}_2 \mathrm{O}(l) \rightarrow \mathrm{H}_2 \mathrm{O}(\mathrm{g})\)

Therefore, in the vaporization of1 mol of water, Δn = +1.

Hence, for the vaporization of 5 mol water, Δn = +5.

So, the amount of heat required to vaporize 90 g (5 mol) of water =540 x 90 = 48600 cal.

As the vaporization process occurs at constant pressure (1 atm), the heat absorbed = enthalpy change.

∴ The change in enthalpy in the vaporization of 90g of water, ΔH = 48600 cal

∴ The change in internal energy in the vaporization of 90gofwater, ΔH = ΔH-ΔnRT

= 48600- 5 × 1.987 × (273 + 100) = 44894.24 cal .

Question 4. Assuming the reactant and product gases obey its ideal gas law, calculate the change in internal energy (AE) at 27°C for the given reaction:
Answer:

⇒ \(\mathrm{C}_2 \mathrm{H}_4(\mathrm{~g})+3 \mathrm{O}_2(\mathrm{~g}) \rightarrow 2 \mathrm{CO}_2(\mathrm{~g})+2 \mathrm{H}_2 \mathrm{O}(l) ;\)

In tlui rimdlon, Δn= 2-1=1.

We know, ΔH = ΔU+ΔuRT

As given, ΔH = 498.3 kj. mol-1 , T = 298 K

∴ 498.3 = ΔH + (1 × 8.314 × 10-3 × 298) or, ΔH = 495.8 kJ

The bond energy of the O2 molecule = 495.8 kj.mol-1

In the reaction , Δn =2- (1 + 3)= -2

we know ΔH+ ΔnRT

Or, 337= ΔU-2 × 1.987 × 10-3 × 300

Or, ΔU =-335.8kcal

CBSE Class 11 Chemistry Notes For Chapter 8 Redox Reactions

Balancing Of Chemical Equations Involving Redox Reactions

Redox reaction can be balanced with the help of two methods. These are the

  1. Ion-electron method
  2. Oxidation number method.

Ion-electron method

Jade and Lamer in 1927 introduced this method. In the ion-electron method, only the molecules and ions which participate in the chemical reaction are shown.

In balancing redox reactions by this method the following steps are followed: 

  • The reaction is written in ionic form.
  • The reaction is divided into two half-reactions with the help of ions and electrons. One half-reaction is for oxidation reaction and the other half-reaction is for reduction reaction.
  • While writing the oxidation reaction, the reducing agent and the oxidised substance are written respectively on the left and right of an arrow signing are written respectively on the left and right of the arrow sign
  • To denote the loss of electrons in oxidation half-reaction, the number of electrons (s) is written on the right of the arrow sign (→). While writing the reduction half-reaction, the number of electrons (s) gained is written on the left arrow sign ( →).

Thus, the oxidation half-reaction is:

Reducing agent – Oxidised substance +ne [where n = no. of electron (s) lost in oxidation reaction] Thus reduction half-reaction is Oxidising agent + ne Reduced substance [where n = no. of electron(s) gained reduction reaction] 2Cr3+

Then each half-reaction is balanced according to the following steps:

In each of the half-reactions, the number of atoms other than H and O -atoms on both sides ofthe arrow sign is balanced.

If a reaction takes place in an acidic medium, for balancing the number of H and O-atoms on both sides of the arrow sign, H2O or H+ is used. First, oxygen atoms are balanced by adding H2O molecules to the side that needs O-atoms.

Then to balance the number of H-atoms, two H+ ions (2H+) for each molecule of water are added to the opposite side (i.e., the side deficient in hydrogen atoms) of the reaction occurs in an alkaline medium, for balancing the H and O -atoms, H2O or OH ion is used.

  • Each excess oxygen atom on one side of the arrow sign is balanced by adding one water molecule to the same side and two ions to the other side.
  • If the hydrogen atom is still not balanced, it is then balanced by adding one OH for every excess hydrogen atom on the side of the hydrogen atoms and one water molecule on the other side of the arrow sign in a half-reaction, both H+ and OH ions cannot participate.
  • The charge on both sides of each half-reaction is balanced. This is done by adding an electron to that side which is a deficient negative charge.
  • To equalise the number of electrons of the two half-reactions, any one of the reactions or both reactions should be multiplied by suitable integers.
  • Now, the two half-reactions thus obtained are added. Cancelling the common term(s) on both sides, the balanced equation is obtained.

Examples:

1. In the presence of H2SO4, potassium dichromate (K2Cr2O2) and ferrous sulphate (FeSO4) react together to produce ferric sulphate [Fe2(SO4)3] and chromic sulphate [Cr2(SO4)3].

Reaction:

K2Cr2O7 + FeSO4 + H2SO4→ K2SO4 + Cr2(SO4)3 + Fe2(SO4)3 + H2O

The reaction can be expressed in ionic form as:

Cr3+ + Fe3+ + H2O

Oxidation half-reaction: Fe2+→Fe3++ e ……………………(1)

Reduction half-reaction: Cr2O72-+ Cr3+ ……………………(2)

1. Balancing the Cr -atom: Cr2O72-– Cr3+ 7H2O

2.To equalise the number of O -atoms on both sides, 7 water molecules are to be added to the right side. 2Cr3+ + 7H2O

⇒ \(\mathrm{Cr}_2 \mathrm{O}_7^{2-} \longrightarrow 2 \mathrm{Cr}^{3+}+7 \mathrm{H}_2 \mathrm{O}\)

∴ One water molecule is required for each O-atom.

3. To balance H-atoms on both sides, 14H+ ions are to be added to the left side.

⇒ \(\mathrm{Cr}_2 \mathrm{O}_7^{2-}+14 \mathrm{H}^{+} \longrightarrow 2 \mathrm{Cr}^{3+}+7 \mathrm{H}_2 \mathrm{O}\)

∴ 2H+ ions are required for each water molecule.

4. For equalising the charge on both sides, 6 electrons are to be added to the left side.

⇒ \(\mathrm{Cr}_7 \mathrm{O}_7^{2-}+14 \mathrm{H}^{+}+6 e \longrightarrow 2 \mathrm{Cr}^{3+}+7 \mathrm{H}_2 \mathrm{O}\)

Now, for balancing the number of electrons in oxidation and reduction half-reactions, the balanced oxidation half-reaction is multiplied by 6 and the balanced reduction half-reaction by 1. Then these two equations are added.

CBSE Class 11 Chemistry Notes For Chapter 8 Redox Reaction Ionic form

This balanced equation has been expressed in ionic form. This equation can be represented in molecular form as:

6FeSO4 + K2Cr2O7 + 7H2SO4 → 3Fe2(SO4)3 + Cr2(SO4)3+ K2SO4+ 7H2O

∴ For 2H+ ions, one H2SO4 molecule is required

2. In presence of H2SO4, KMnO4 and FeSO4 react together to produce MnSO4 and Fe2(SO4)3.

Reaction: KMnO4 + FeSO4 + H2SO4 → K2SO4 + MnSO4+ Fe2(SO4)3 + H2O

The equation can be expressed in ionic form as:

MnO4 + Fe2+ + H+→-Mn2+ + Fe3+ + H2O

Oxidation half-reaction: Fe2+ — Fe3+ + e ………………………..(1)

Reduction half-reaction: MnO4 + 8H+ + 5e → Mn2+ + 4H2O………………………..(2)

To balance the number of electrons lost in the oxidation half-reaction, the oxidation half-reaction is multiplied by 5 and then the two reactions are added.

CBSE Class 11 Chemistry Notes For Chapter 8 Redox Reaction Molecule Contains Fe atoms

As one Fe2(SO4)3 molecule contains two Fe -atoms, the equation is multiplied by 2

10Fe2+ + MnO4 + 16H+ →10Fe3+ + 2Mn2+ + 8H2O

This is the balanced equation in ionic form. This equation when expressed in molecular form becomes

10FeSO4 + 2KMnO4+ 8H2SO4 →  5Fe2(SO4)3 + 2MnSO4 + 8H2O

Equalising the number of atoms of different elements and the sulphate radicals we get,

10FeSO4+ 2KMnO4 + 8H2SO4 → 5Fe2(SO4)3 + 2MnSO4 + K2SO4 + 8H2O

This is a balanced equation of the given reaction in molecular form.

3. In the reaction between K2Cr2O7 acidified with dilute H2SO4  and KI, Cr2(SO4)3 and I2 are formed.

K2Cr2O7+KI + H2SO4 → K2SO4 + Cr2(SO4)3 + I2 + H2O

The equation can be expressed in ionic form as— Cr2O72-+I + H+ — Cr3+ + I2 + H2O

Oxidation half-reaction: 2I→ I2 + 2e……………..(1)

Reduction half-reaction: Cr2O7 2-+ I+14H+ + 6e — 2Cr3+ + 7H2O ……………………….(2)

To balance the electrons, equation (1) is multiplied by 3 and added to equation (2). Thus the equation stands as—

CBSE Class 11 Chemistry Notes For Chapter 8 Redox Reaction The Equation balanced in Ionic form

This is the balanced equation of the reaction in ionic form. The above ionic reaction can be expressed in molecular form as follows

6KI + K2Cr2O7 + 7H2SO4→3I2 + Cr2(SO4)3 + 7H2O

Equalising the number of atoms of potassium and sulphate radical on the left and right sides, we have,

6KI + K2Cr2O7+ 7H2SO4 → 3I2 + Cr2(SO4)3 + 4K2SO4 + 7H2O

4. In the reaction between KMnO4, acidified with dilute H2SO4 and oxalic acid (H2C2O4), MnSO4 and CO2 were produced.

Reaction: KMnO4 + H2C2O4 + H2SO4 → K2SO4 + MnSO4 + CO2 + H2O

Oxidation half-reaction: C2O4→  2CO42-+ 2e ……………………..(1)

Reduction half-reaction: MnO4 +8H++ 5e → Mn2++ 4H2O……………………..(2)

Now, multiplying equation (1) by 5 and equation (2) by 2 and then adding them, we get,

5C2O4 2-+ 2MnO4 + 16H++10CO2 + 2Mn2+ + 8H2O

This Is the balanced equation of the given reaction in molecular form.

5H2C2O4 + 2KMnO4+ 3H2SO4→ 10CO2 + Mn2+ +8H2O

Equalising the number of atoms of potassium and sulphate radical we get

5H2C2O4 + 2KMnO4 + 3H2SO4 → 10CO2 + 2MnSO4 + K2SO4 + 8H2O

5. In NaOH solution, Zn reacts with NaNO3 to yield Na2ZnO2, NH3 and H2O.

Reaction:

Zn + NaNO3 + NaOH — Na2ZnO2 + NH3 + H2O The equation can be expressed in ionic form as—

Zn + NO + OH→ ZnO2 →+ NH3 +H2O

Oxidation half-reaction: Zn + 4OH→ ZnO2 + 2H2O + 2C ……………………..(1)

Reduction half-reaction: NO3 + 6H2O + 8C — NH3 + 9OH……………………..(2)

Now multiplying equation (1) by 4 and then adding to equation (2), we get,

4Zn + 16OH- + NO, + 6H2O→ 4ZnO2 + NH3 + 90H- + 8H2O

Or, 4Zn + 7OH+ NO3→ 4ZnO2 + NH3 + 2H2O

It is the balanced equation of the reaction in ionic form. Expressing the above equation in molecular form

4Zn + 7NaOH + NaNO3→ 4Na2ZnO2 + NH3 + 2H2O

It is the molecular form of the balanced equation of the reaction.

6. In the presence of HNO3, sodium bismuthatic (NaHO3) reacts with Mn(NO3)2 to produce coloured sodium permanganate (NaMnO4) and itself gets reduced to bismuth nitrate.

Reaction: NaBIO3 + Mn(NO3) + UNO2 →NaMnO4 + Bi(NO3) + H2O The equation can be expressed in ionic form as— BIO2 + Mn2+ → Bl3+ + MnO4 + H2O

Oxidation half-reaction: Mn2+ + 4H2O → MnO4+8H+→+5e ……………………(1)

Reduction half-reaction: BiO3 + 6H+ + 2e — Bi3+ + 3H2O…………………….(2)

Multiplying equation (1) by 2 and equation (2) by 5 and then adding them we get—

2Mn2+ + 8H2O + 5BiO3 +30H+→ 2MnO4 + 16H+ + 5Bi3+ +15H2O

2Mn2+ + 5BiO3 + 14H+→ 5Bi3++ + 2MnO4  +7HO

This is the balanced ionic equation of the reaction. The equation in the molecular form stands as—

2Mn(NO3)2 + 5NaBiO3+ 14HNO3 →  5Bi(NO3)3 + 2NaMnO4 + 7H2O

Ionic reaction: IO3 + I+ H+→ I2 + H2O

Oxidation half-reaction: 2I → I2 + 2e ……………………….(1)

Reduction half-reaction: 2 IO3 + 12H++ 10 e → I2 + 6H2O ……………………….(2)

Multiplying equation (1) by 5 and then adding to equation (2) we get,

10I + 2IO3+ 12H+ → 6I2+ 6H2O or, 5I + 1O3+ 6H+ — 3I2 + 3H2O

This is the balanced ionic equation of the reaction.

Oxidation number method

In any redox reaction, the increase in the oxidation number of some of the atoms is balanced by the decrease in the oxidation number of some other atoms.

The steps which are to be followed while balancing the oxidation-reduction equation by this method are given below— After identifying the oxidant and reductant, the skeleton equation for the reaction is written.

  • The elements of the reactants and the products changing oxidation number are identified and the oxidation number of the concerned atoms is mentioned.
  • The reactant in which the element undergoes a decrease in oxidation number is the oxidant, while the reactant in which the element undergoes an increase in oxidation number is the reductant.
  • As oxidation and reduction are complementary to each other, die increase and decrease in oxidation numbers should necessarily be equal, For this reason, the respective formulae of the oxidants and reductants are multiplied by a possible suitable integer so that the changes in oxidation numbers arc equalised.
  • For balancing the equation, it may sometimes be necessary to multiply the formula of other substances participating in the reaction by a suitable integer.
  • If the reactions are carried out in an acidic medium, then, to balance the number of O -atoms, one molecule of Ois added for each O -atom to the side of the equation deficient in oxygen.

To balance the number of -atoms, H+ ions are added to the side deficient in hydrogen.

In case of a reaction occurring in an alkaline medium, to balance the number of O -atoms on both sides of the equations, for each O -atom one molecule of water is added to the side deficient in O -atoms and to the opposite side two OH- ions for each water molecule are added.

Again for balancing the number of FIatoms on both sides of the equation, for each 2 -atom one OH ion is added to the side which contains excess 2 -atoms and the same number of FI2O molecules are added to the other side.

Example

1. Copper dissolves in concentrated HNO3 to form Cu(NO3)2, NO2 and H2O

Reaction:

CBSE Class 11 Chemistry Notes For Chapter 8 Redox Reactions Copper Dissolves In Concentarated HNO3

In the given reaction, the increase in oxidation number of Cu -atom =(+2)-0 = 2 unit (oxidation) and the decrease in oxidation number of N -atom =(+5)-(+4) = 1 unit (reduction).

To nullify the effect of increase and decrease in the oxidation numbers, the ratio of the number of Cu -atoms and Cu(NO3)2  molecules in the reaction should be 1:2. So the equation may be written as

Cu + 2HNO3 → Cu(NO3)2 + 2NO2 + H2O

Now, to produce one molecule of Cu(NO3)2 two NO2 radicals i.e. two molecules of UNO2 are required. Hence in the reaction further addition of two molecules of HNO3 is necessary. So the balanced equation is expressed as

Cu + 4HNO3→ Cu(NO3)2 + 2NO2 + 2H2O

Now, to produce one molecule of Cu(NO3)2, two NO3 radicals i.e. two molecules of UNO2 are required.

Hence in the reaction further addition of two molecules of HNO2 is necessary. So the balanced equation is expressed as

Cu+4HNO3 Cu(NO3)→ 2+2NO2+2H2O

When H2S gas is passed through chlorine water H2SO4 is produced.

Reaction:

CBSE Class 11 Chemistry Notes For Chapter 8 Redox Reactions When H2S gas Is Passed Through Chlorine Water

In this reaction, an increase in the oxidation number of S = (+6) — (— 2) = 2 units (oxidation) and a decrease In the oxidation number of Cl = 0 – (— 1 ) I unit (reduction). So decrease In oxidation number for two (‘,1 -atoms or I molecule of Cl2 -2 unit.

To neutralise the effect of Increase and decrease In oxidation number in the given equation, the number of molecules of H2S and Cl2 should be in the ratio of 2: i.e., 1: <1.

Therefore, the equation becomes

H2S+4CI2+HCl+H2SO4

Balancing the number of 11 and O -atoms on both sides gives the balanced equation —

3. NH3 gas when passed over heated Cut) produces Cu, N2 and H2O.

CBSE Class 11 Chemistry Notes For Chapter 8 Redox Reactions NH3 Gas When Passed over heated

In this reaction, increase In oxidation number of N=0-(-3) = 3 unit (oxidation) and decrease In oxidation number of Cu =(+2)-0 = 2 unit (reduction). As, in a redox reaction, the total increase in oxidation number is equal to the total decrease In oxidation number, the number of molecules of CuO and NH3 in the reaction should be in the ratio of 3:2. Hence, the balanced equation will be—

3CuO+2NH3→3Cu+N2+3H2O

4. In the reaction between KMnO4 and H2O2, the products obtained were K2SO2 MnSO2, H2O And O2.

Reaction:

CBSE Class 11 Chemistry Notes For Chapter 8 Redox Reactions The Reaction Between KMNO4 And H2O2

In this reaction increases in oxdination number of O = 0-(-1)=1 (oxidaxtion) and dexrease in oxidation number of MN= (+7)-(+20)

= 5 unit (reduction).

The total increase in the oxidation number of two 0 -atoms presents one molecule of H2O2

To balance the decrease and increase in oxidation numbers, the ratio of the number of KMnO2 and H2O, molecules in the equation for the reaction will be 2:5.

Again from 2 molecules of KMnO4 and 5 molecules of H2O2, 2 molecules of MnSO2 and 5 molecules of O2 are produced respectively. Thus the equation becomes—

2KMnO4 + 5H2O2+ H2SO4→ K2SO4+ 2MnSO4 + 5O2 + H2O

Again, for the formation of 1 molecule of K2SO4 and 2 molecules of MnSO4, three SO4– radicals are required and hence three H2SO4 molecules are necessary on the left-hand side. Besides this, the total number of H-atoms in 5 molecules of H2O2 and 3 molecules of H2SO4 = 16.

These H-atoms produce water molecules. Therefore, 8 molecules of H2O are to be placed on the right-hand side. So the balanced equation will be—

2KMnO4 + 5H2O2 + 3H2SO4 → K2SO4 + 2MnSO4 + 5O2+ 8H2O

5. White phosphorus and concentrated NaOH react together to yield NaH2PO2 and PH3. Reaction

CBSE Class 11 Chemistry Notes For Chapter 8 Redox Reactions White Phosphorus And Concentrated NaOH

The increase in oxidation number of P [P to NaH2PO2 ] = +1- 0 = 1 unit (oxidation). The decrease in oxidation number of P [P to PH3] = 0-(-3) = 3 unit (reduction). To balance the increase and decrease in oxidation number, three P atoms for oxidation and one P -atom for reduction are required. Thus four P -atoms are necessary.

Now, in the oxidation of P, NaH2PO2 and its reduction, PH3 are formed. So the oxidation of three P atoms forms 3 molecules of NaH2PO9 and for this, three NaOH molecules are required. Again 1 atom of P reduction produces 1 molecule of PH3. So the equation will be

P4+3NaOH + H2O→ 3NaH2PO2 + PH3

On the right side of the equation, there are 6 oxygen atoms, out of which 3 atoms will come from 3 molecules of NaOH and for the rest three atoms, 3 molecules of H2O will be necessary. Hence, the balanced equation will be

P4+ 3NaOH + H2O → 3NaH2PO2 + PH3

6. In NaOH solution, Zn reacts with NaNO3 to yield Na2ZnO2, NH3 and H2O.

Reaction:

CBSE Class 11 Chemistry Notes For Chapter 8 Redox Reactions In NaOH Solution Zn reacts With NaNO3 To yeild

In the reaction, an increase in the oxidation number of Zn =(+2) -0 = 2 unit (oxidation) and a decrease in the oxidation number of N =(+5)-(-3) = 8 unit (reduction). As the increase and decrease in oxidation number in the reaction must be equal, the number of Zn -atoms and the number of molecules of NaNO3 should be in the ratio of 4:1. Now, 1 molecule of NaNO3 and 4 atoms of Zn produce 1 molecule of NH3 and 4 molecules of Na2ZnO2 respectively. Therefore the reaction is—

4Zn + NaNO3 + NaOH →4Na2ZnO2 + NH3 + H2O

Again formation of 4 molecules of Na2ZnO2 requires 8 Na -atoms, out of which 1 atom is supplied by 1 molecule of NaNO3. Additional 7 Na -atoms come from NaOH on the left side. To balance H -atoms on both sides, 1 H2O molecule is to be placed on the right side. Thus the balanced equation will be —

4Zn + NaNO3 + 7NaOH →4Na2ZnO2 + NH3 + 2H2O

7. In the reaction between Cr2O3 and Na2O2, Na2CrO4 and NaOH are produced.

Reaction:

CBSE Class 11 Chemistry Notes For Chapter 8 Redox Reactions In The Reaction Between Cr2O3 And Na2O2

In this reaction, an increase in the oxidation number of Cr = (+6)- (+3) = 3 unit (oxidation) and a decrease in the oxidation number of O =(- 1 )-(- 2) = 1 unit (reduction). Thus a total increase in the oxidation number of two Cr -atoms = 3 × 2 = 6 units and the total decrease in the oxidation number of two O -atoms = 1× 2

= 2 units.

To balance the increase and decrease in oxidation number, the ratio of Cr2O3 and Na2O2 should be =1:3. Now 2 molecules of Na2CrO4 are produced from 1 molecule of Cr2O3. Hence the equation will be as follows—

Cr2O3+3Na2O2+H2O→ 2Na2CrO4+NaOH

If Na, H and O- atoms are balanced on both sides, the balanced equation will stand as

Cr2O3+ 3Na2O2 + H2O→ 2Na2CrO4 + 2NaOH

8. White phosphorus reacts with copper sulphate solution to produce Cu, H3PO4 and H2SO4.

Reaction:

CBSE Class 11 Chemistry Notes For Chapter 8 Redox Reactions White Phosphorus Reacts With Copper Sulphate Solution

In this reaction, an increase in the oxidation number of P = (+5)-0 = 5 unit (oxidation) and a decrease in the oxidation number of Cu =(+2)-0 = 2 unit (reduction).

Since the increase and decrease in oxidation number must be equal, in the given reaction, the ratio of the number of atoms of P and the number of CuSO4 molecules should be in the ratio of 2: 5. Again 2 molecules of H3PO4 and five Cu -atoms will be produced respectively from two P atoms and five CuSO4 molecules. As a result, the equation becomes—

2P + 5CuSO4 + H2O→ 5Cu + 2H3PO4 + H2SO4

To balance the number of SO²‾4 radicals on both sides of the equation, 5 molecules of H2SO4 are to be added to the right-hand side ofthe equation.

2P + 5CuSO4 + H2O→5Cu + 2H3PO4 + 5H2SO4

Now, the total number of H-atoms present in 2 molecules of H3PO4 and 5 molecules of H2SO4 =16. So, for balancing the number of H-atoms, 8 water molecules are to be placed on the left-hand side. So, the balanced equation will be

2P + 5CuSO4 + 8H2O→5Cu + 2H3PO4 + 5H2SO4

9. Aluminium powder when boiled with caustic soda solution yields sodium aluminate and hydrogen gas.

Reaction:

CBSE Class 11 Chemistry Notes For Chapter 8 Redox Reaction Sodium Aluminate

Aluminium is oxidised in this reaction to produce sodium aluminate. On the other hand, the H -atoms of NaOH and H2O are reduced to produce H2. Therefore, the change in oxidation number in the reaction may be shown as follows—

CBSE Class 11 Chemistry Notes For Chapter 8 Redox Reactions The Change In Oxidation Number In The Reaction

The increase in oxidation number of A1 = (+3) -0 = 3 unit (oxidation), the decrease in oxidation number of 1 H atom of NaOH molecule \(=(+1)-\left(\frac{1}{2} \times 0\right)\) (reduction) and decrease in oxidation number of 2 H -atoms
of water molecule = 2 x (+1) -2×0 = 2 unit(reduction).

Hence, the total decrease in oxidation number for the Hatoms in 1 molecule of NaOH and 1 molecule of H2O =3 unit.

Since, in a chemical reaction, the increase and decrease in oxidation number are the same, the ratio of the number of A1 atoms, NaOH molecule and water molecules in the given reaction should be =1: 1: 1.

⇒ \(\mathrm{Al}+\mathrm{NaOH}+\mathrm{H}_2 \mathrm{O} \longrightarrow \mathrm{NaAlO}_2+\frac{1}{2} \mathrm{H}_2+\mathrm{H}_2\)

Hence, the given reaction may be represented as:

Now, to express the number of molecules of reactants and products in terms of whole numbers, both sides of the equation should be multiplied by 2.

So, the balanced equation will be as follows:

⇒ \(\mathrm{Al}+\mathrm{NaOH}+\mathrm{H}_2 \mathrm{O} \longrightarrow \mathrm{NaAlO}_2+\frac{1}{2} \mathrm{H}_2+\mathrm{H}_2\)

Determination of equivalent mass of an element or compound in disproportionation reaction:

If in oxidation and reduction reaction, the change in oxidation number of any element or an element of any compound participating in a disproportionation reaction be n1 and n2 respectively and M be the molecular mass of that element or compound, then the equivalent mass of that element or compound \(=\frac{M}{n_1}+\frac{M}{n_2}\)

In oxidation reaction (P4— change in oxidation number of each P -atom = 1 unit. So the total change in oxidation number of four P-atoms = 4 × 1 =4 units.

In the reduction reaction, (P4→PH3), the change in oxidation number of each P-atom is 3 units. So the total change in oxidation number of four P-atoms = 4×3 = 12 units.

Thus in this reaction, the equivalent mass of P4.

⇒ \(\frac{M}{4}+\frac{M}{12}=\frac{4 \times 31}{4}+\frac{4 \times 31}{12}=31+10.33 \text {= } 41.33\)

∴ The atomic mass of p = 31

Redox Titration

A process by which a standard solution of an oxidant (or a standard solution of a reductant) is completely reacted with a solution of an unknown concentration of a reductant (or with a solution of an unknown concentration of an oxidant) in the presence of a suitable indicator is called redox titration.

In a redox titration, an oxidant (or a reductant) reacts completely with an equivalent amount of a reductant (or an oxidant). Therefore, in a redox titration, the number of grams equivalent of oxidant = number of grams equivalent of reductant.

Types of redox titrations

1. Permanganometry titration

A titration in which KMnO4 solution is used as the standard solution. In this titration, no indicators are needed.

Example:

The amount of iron present in an acidic ferrous ion (Fe2+) solution can be estimated by titrating the solution with a standard solution of KMnO4.

Reaction:

MnO4 + 5Fe2+ + 8H+ → Mn2+ + 5Fe3+ + 4H2O …………………….(1)

Oxidation reaction: Fe2+→ Fe3+ + e

Reduction reaction: MnO4 + 8H+ + 5e → Mn2+ + 4H2O

So, in this reaction, the equivalent mass of Fe2+ — an atomic mass of Fe and the equivalent mass of KMnO4 \(=\frac{1}{5} \times\) Molecular or formula mass of KMnO4

According to the reaction (1), 1 mol of KMnO4 = 5 mol of Fe2+ ions or, 1000 mLof 1 mol of KMnO4 solution = 5 × 55.85g of Fe2+ ions or, 1 mLof l(M) KMnO4 solution = 0.2792g of Fe2+ ions mL of 5(N) KMnO4 solution = 0.2792g of Fe2+ ions. [In the given reaction, the normality of KMnO4 solution is five times its molarity.]

lmL of (N) KMnO4 solution = 0.05585g of Fe2+ ions

2.  Dichromatometry titration

A ptration in which a standard solution of potassium dichromate (K2Cr2O7) is used.

In this titration, sodium or barium diphenylamine sulphonate or diphenylamine is used as an indicator.

Example:

The amount of iron present in an acidic ferrous ion (Fe2+) solution can be calculated by titrating the solution with a standard solution of K2Cr2O7.

Reaction: 

Cr2O7+ 14H+ + 6Fe2+→ 2Cr3++ 6Fe2+ + H2O …………….(1)

In reaction (1), the equivalent mass of Fe2+ is equal to the atomic mass of Fe, & the equivalent mass of K2Cr2O7 is equal to one-sixth of its molecular or formula mass.

According to the reaction (1), 1 mol of K2Cr2O7 H 6mol of Fe2+ ions

Or, 1000mL of 1M K2Cr2O7 = 6 × 55.85 g of Fe2+ ions

Or, lmLof1M K2Cr2O7 solution s 0.3351g of Fe2+ ions

Or, lmL of 6N K2Cr2O7 solution s 0.3351g of Fe2+ ions

[In the given reaction, the normality of K2Cr2O7 solution is six times its molarity.]

lmL of IN K2Cr2O7 solution = 0.05585g of Fe2+ ions

3. Iodometry titration

In this titration, KI in excess is added to a neutral or an acidic solution of an oxidant. Consequently, the oxidant quantitatively oxidises I ions (reductant), to form I2. The liberated I2 is then titrated with a standard Na2S2O3 solution using starch as an indicator.

The amount of liberated iodine is calculated from the volume of standard Na2S2O3 solution consumed in one titration. After the amount of liberated iodine is known, one can calculate the amount of oxidant by using the balanced chemical equation for the reaction of oxidant with iodine.

Example:

Iodometric titration is often used for quantitative estimation of Cu2+ ions. The addition of excess KI to a neutral or an acidic solution of Cu2+ ions results in oxidation of 1 to I2 and reduction of Cu2+ to Cu+.

So, in the reaction(l), the equivalent mass of \(\mathrm{Cu}^{2+}=\frac{2 \times \text { atomic mass of } \mathrm{Cu}}{2}=\text { atomic mass of } \mathrm{Cu}\)

The reaction of I2 with Na2S2O3 is:

⇒  \(2 \mathrm{~S}_2 \mathrm{O}_3^{2-}+\mathrm{I}_2 \rightarrow \mathrm{S}_4 \mathrm{O}_6^{2-}+2 \mathrm{I}^{-}\)

In this reaction, Oxidation reaction:

⇒  \(2 \mathrm{~S}_2 \mathrm{O}_3^{2-} \rightarrow \mathrm{S}_4 \mathrm{O}_6^{2-}+2 e\)

Reduction reaction: I2 + 2e → 2I

Therefore, the equivalent mass of Na2S2O3

⇒ \(\frac{2 \times \text { molecular or formula mass of } \mathrm{Na}_2 \mathrm{~S}_2 \mathrm{O}_3}{2}\)

= molecular or formula mass of Na2S2O3

Equivalent mass of I2 \(=\frac{\text { molecular mass of } \mathrm{I}_2}{2}=\text { atomic mass of } \mathrm{I}\)

According to the reactions (1) and (2), 2mol of Cu2+ = 1 mol of I2 and 2 mol of Na2S2O3 s 1 mol of I2

Therefore, 2mol of Na2S2O3= 2 mol of Cu2+ or, 1 mol of Na2S2O3 = l mol of Cu2+ = 63.5g of Cu2+ or, l mol of lM Na2S2O3 solution = 63.5 g of Cu2+ or, 1 mol of IN Na2S2O3 solution = 63.5gof Cu2+ [As in the reaction of Na2S2O3 with I2, the equivalent mass of Na2S2O3 is equal to its molecular mass].

CBSE Class 11 Chemistry Chapter 7 Equilibrium Short Question And Answers

Question 1. The reaction Fe2O3(s) + 3CO(gH→2Fe(s) + 3CO2(g) is carried out separately in a closed vessel and an open vessel. In which case do you expect a higher yield of CO2(g)?
Answer:

If the reaction Fe2O3(s) + 3CO(g)→2Fe(s) + 3CO2(g) is carried out in a closed vessel, an equilibrium is established between the reactants and the products. As a result, the reaction vessel always contains a mixture of reactants and products.

On the other hand, if the reaction is carried out in an open vessel, CO2(g) formed in the reaction diffuses out from the vessel and mixes with the air and does not have the opportunity to react with Fe(s).

As a result, the reaction becomes irreversible and goes to completion. At the end of the reaction, the vessel only contains Fe(s). Since the reaction reaches completion in an open vessel, the yield of CO2(g) will be higher in this condition.

Question 2. If a reversible reaction is carried out in a closed vessel, the reactant(s) is/are never used up completely. Explain the reaction with an example.
Answer:

When a reversible reaction is carried out in a closed vessel, an equilibrium is established between the reactants and the products.

As a result, the reaction system always contains a mixture of reactants and products. In other words, a reversible reaction occurring in a closed vessel never gets completed. Consequently, the reactants are never used up.

Question 3. 2BrP2(g) ⇌ Br2(g) + 5F2(g); At constant temperature, how the increase in pressure will affect the following at equilibrium— Equilibrium constant, Position of the equilibrium, and yield of the product?
Answer:

Pressure does not affect the magnitude of the equilibrium constant.

The given reversible reaction involves a decrease in several gas molecules in the backward direction. So, increasing pressure at the equilibrium of the reaction will favor the backward reaction Consequently, the yield of the product will decrease.

Question 4. Write the conjugate bases of the following acids and give the reason: HN3, CH3OH, [Al(H2O)6]3+, NH4+, HPO42-, H2O2, OH
Answer:

According to the Bronsted-Lowry concept, an acid is a substance that can donate protons. The species formed when an acid donates a proton is called the conjugate base of the acid. The conjugate base of an acid has one fewer H-atom than the acid.

Therefore, the conjugate bases of HN3, CH3OH, [Al(H2O)6]3+, NH4+, HPO42-, H2O2 and OH are N3, CH3O, [Al(H2O)5OH]2+, NH3, PO3-4, HO2 and O-2, respectively.

Question 5. Write the conjugate acids of the following bases and give the reason: OH, H2PO4, O2-, HS, SO2-3, H2O, HCO3, NH2, NH3, H, C6H5NH2, S2O82- CO32-
Answer

According to the Bronsted-Lowry concept, a base is a proton acceptor. When a base accepts a proton, the conjugate acid of the die base is formed. The conjugate acid of a base contains one more H-atom than the base.

Therefore, the conjugate acids of OH, H2PO4 , O2-, HS, SO23, H2O, HCO3, NH2 , NH3, H, C6H5NH2 , S2O82- and CO32-– are H2O , H3PO4 , OH , H2S, HSO3, H3O+, H2CO3, NH3, NH4++, H2, C6H5NH+3, HS2O8 and HCO3 respectively.

Question 6. To find out the equilibrium constant (K) of a reaction, it is compulsory to mention the balanced equation of the reaction—why?
Answer:

The value of the equilibrium constant (K) depends on how the balanced equation of the reaction is written, example the formation of H2 (g) from H2 (g) and I2 (g) can be written in two different ways

⇒ \(\mathrm{H}_2(g)+\mathrm{I}_2(g) \rightleftharpoons 2 \mathrm{HI}(g) \text { (2) } \frac{1}{2} \mathrm{H}_2(g)+\frac{1}{2} \mathrm{I}_2(g) \rightleftharpoons \mathrm{HI}(g)\)

Both 1 and 2 express the same reaction but the coefficients of reactants and products are different. As a result, the value of the equilibrium constant (K) for the reaction will not be the same in the above two cases.

Question 7. Find Out Kp/Kc for the solutions \(\mathrm{CO}(g)+\frac{1}{2} \mathrm{O}_2(g) \rightleftharpoons \mathrm{CO}_2(g)\)
Answer:

We know that \(K_p=K_c(R T)^{\Delta n}.\)

For the given reaction \(\Delta n=1-\left(1+\frac{1}{2}\right)=-\frac{1}{2}\)

Thus \(K_p=K_c(R T)^{-\frac{1}{2}}\)

⇒ \(\frac{K_p}{K_c}=\frac{1}{\sqrt{R T}}\)

Question 8. By what factor will the concentration of H3O+ ions in an aqueous solution be increased or decreased if its pH is increased by one unit?
Answer:

If the pH of an aqueous solution be x, then [H3O+] in the solution = 10-pH

= 10-x mol.L-1

Increasing the pH of this solution by one unit makes

pH =  1 + x.So, (H3O+) In the solution

= 10-pH = 10-(1+x)

= \(\frac{10^{-x}}{10} \mathrm{~mol} \cdot \mathrm{L}^{-1}\)

Question 9. Why is the ionic product of water at 50 greater than that at 25°C?
Answer:

Ionisation of water \(\left[2 \mathrm{H}_2 \mathrm{O}(l) \rightleftharpoons \mathrm{H}_3 \mathrm{O}^{+}(a q)+\mathrm{OH}^{-}(a q)\right]\)

Is an endothermic process. The equilibrium constant referring to the ionization equilibrium of water is called the ionic product of water (Kw). As the process is endothermic, Kw increases with the temperature rise. Thus, Kw of water at 50 °C is greater than that at 25 °C.

Question 10. The pH of solution A is twice that of solution B. If the concentrations of H3O+ ions in A and B are x (M) and y (M), respectively, then what is the relation between x and y?
Answer:

Given:

pH of the solution A = 2 × pH of the solution B,

⇒ \(\left[\mathrm{H}_3 \mathrm{O}^{+}\right]_A=x \mathrm{~mol} \cdot \mathrm{L}^{-1} \text { and }\left[\mathrm{H}_3 \mathrm{O}^{+}\right]_B=y \mathrm{~mol} \cdot \mathrm{L}^{-1} \text {. }\)

∴ \(-\log _{10}\left[\mathrm{H}_3 \mathrm{O}^{+}\right]_A=2 \times-\log _{10}\left[\mathrm{H}_3 \mathrm{O}^{+}\right]_B\)

Or, \(x=y^2 \text { or, } y=\sqrt{x}\)

 

CBSE Solutions For Class 10 Maths

 

CBSE Class 10 Maths Solutions

Ascending and Descending Tracts Of The Spinal Cord

Ascending Descending Tracts Of The Spinal Cord Multiple Choice Questions

Question 1. The following statements regarding sensory pathways are true except

  1. Ascending spinal tracts are sensory
  2. Sensory pathways usually consist of two sensory neurons
  3. Some somatic impulses do not reach the level of consciousness
  4. The cell body of most of the first-order sensory neurons is located outside the CNS
  5. The cell bodies of the mesencephalic nucleus lie within the CNS though it contains first-order sensory neurons

Answer: 2. Sensory pathways usually consist of two sensory neurons

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Question 2. Which of the following statements is true?

  1. The first-order sensory neuron of the sensory pathway lies in the dorsal root ganglion of the spinal nerve
  2. The second-order sensory neuron lies in the dorsal grey horn of the spinal cord.
  3. Third-order sensory neurons are located in the thalamus
  4. Axonal processes of second-order sensory neurons, as a general rule, cross to the opposite side.
  5. All ofthe above

Answer: 3. Axonal processes of second-order sensory neurons, as a general rule, cross to the opposite side.

Spinal Tracts

Question 3. Fasciculi gracilis and cuneatus are concerned with except

  1. Conscious proprioception
  2. Fine touch
  3. Vibration and deep pressure
  4. Two-point discrimination
  5. Crude touch

Answer: 5. Crude touch

Question 4. Which of the following statements about the ascending tracts of dorsal white columns is false?

  1. Fasciculus cuneatus is present medial to fasciculus gracilis in the dorsal white column
  2. Fibers of cuneate and gracile fasciculi terminate on the cell bodies of cuneate and gracile nuclei, respectively.
  3. Second-order fibers decussate in the midline to form great sensory decussation.
  4. After decussation, fibers run upwards to form the medial lemniscus.

Answer: 1. Fasciculus cuneatus is present medial to fasciculus gracilis in the dorsal white column

Question 5. Following are the major ascending (sensory) tracts of the lateral white column except

  1. Posterior spinocerebellar
  2. Anterior spinocerebellar
  3. Spinotectal
  4. Anterior spinothalamic
  5. Spino-olivary

Answer: 4. Anterior spinothalamic

Spinal Tracts

Question 6. The following statements are true regarding the anterior spinocerebellar tract except

  1. Anterior Spinocerebellar Tract is a crossed spinocerebellar tract
  2. Anterior Spinocerebellar Tract  carries proprioceptive and exteroceptive impulses
  3. These impulses do not reach the level of consciousness
  4. This pathway consists of three sensory neurons
  5. The fibers of second-order sensory neurons cross twice

Answer: 4. This pathway consists of three sensory neurons

Question 7. The following statements are true regarding the lateral spinothalamic tract except

  1. Lateral Spinothalamic Tract carries the sensation of pain and temperature
  2. Lateral Spinothalamic Tract arises at all the levels of the spinal cord
  3. Lateral Spinothalamic Tract is an uncrossed tract
  4. The second-order neurons are situated in laminae 1, 4 and 5

Answer: 3. It is an uncrossed tract

Question 8. Which of the statements about the anterior corticospinal tract is false?

  1. Anterior Corticospinal Tract is formed mainly by axons arising from the somatomotor cortex
  2. Anterior Corticospinal Tract is a crossed-tract
  3. Anterior Corticospinal Tract terminates on the contralateral anterior horn cells of the spinal cord
  4. Anterior Corticospinal Tract extends throughout the spinal cord

Answer: 2. Anterior Corticospinal Tract  is a crossed tract

Question 9. Which of the following statements about the corticonuclear tract is false?

  1. Fibers terminate on motor nuclei of cranial nerves
  2. Passes through the genu of the internal capsule
  3. Fibers usually terminate on the nuclei of both sides
  4. Injury leads to ‘lower motor neuron type’ of paralysis

Answer: 4. Injury leads to ‘lower motor neuron type’ of paralysis

Spinal Cord Tracts

Question 10. The following facts regarding the rubrospinal tract are true except.

  1. Rubrospinal Tract is a crossed-tract
  2. Rubrospinal Tract arises from the red nucleus
  3. Rubrospinal Tract  is a part of the extrapyramidal system
  4. Rubrospinal Tract descends in the lateral funiculus of the spinal cord
  5. This tract terminates on the neurons of the posterior horn of the spinal cord.

Answer: 5. This tract terminates on the neurons of the posterior horn of the spinal cord.

Brainstem Medulla Multiple Choice Questions

Brainstem Medulla Oblongata Multiple Choice Questions

Question 1. The following statements about the brainstem are true except

  1. It consists of the pons, medulla and cerebellum
  2. It is continuous above with the thalamus, hypothalamus and cerebral hemispheres
  3. It is continuous below with the spinal cord
  4. It lies in posterior cranial fossa

Answer: 1. It consists of the pons, medulla and cerebellum

Question 2. Which of the following statements about the attachment of cranial nerves is false?

  1. The brainstem gives attachment to all the cranial nerves
  2. The nuclei of cranial nerves 3 to 7 are situated deep in the brainstem
  3. Cranial nerves 3 and 4 are attached to midbrain
  4. Cranial nerve 5 is attached to the pons
  5. Cranial nerves 6 to 7 are attached to the medulla

Answer: 1. Brainstem gives attachment to all the cranial nerves

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Question 3. Which of the following statements about the ventral aspect of the medulla is false?

  1. On either side of the anteromedian fissure, there is the presence of a pyramid.
  2. Olive is present lateral to the anterolateral sulcus
  3. The posterolateral sulcus gives attachment to the cranial nerve 7 Ventral aspect of the medulla is related to basisphenoid (clivus)
  4. The anterolateral sulcus is present between the olive and pyramid

Answer: 3. Posterolateral sulcus gives attachment to cranial nerve 7 Ventral aspect of the medulla is related to basisphenoid (clivus)

Question 4. Which of the following statements about the posterior surface of the lower part of the medulla is true?

  • This surface lies between the posteromedian sulcus and the posterolateral sulcus
  • This surface is an upward continuation of fasciculi gracilis and cuneatus
  • Fasciculi gracilis and cuneatus are continuous above as gracile and cuneate tubercles
  • Lateral to fasciculus cuneatus, a swelling is seen that is known as tuberculum cinereum
  • All of the above

Answer: 4. Lateral to fasciculus cuneatus, a swelling is seen that is known as tuberculum cinereum

Question 5. Which of the following statements about the transverse section of the medulla at the level of sensory decussation is false?

  1. This level is cranial to pyramidal decussation
  2. Nuclei gracilis and cuneatus are situated on the posterior aspect of the section
  3. The nucleus of the spinal tract of the trigeminal nerve is situated ventrolateral to the nucleus cuneatus
  4. Nucleus ambiguus is situated in the area of reticular formation
  5. None of the above

Answer: 3. The nucleus of the spinal tract of the trigeminal nerve is situated ventrolateral to the nucleus cuneatus

Question 6. Which of the following facts about the medial longitudinal bundle is false?

  1. In the medulla, it is present posterior to the media lemniscus
  2. It is present anterior to the hypoglossal nucleus
  3. It is present throughout the brainstem in the same paramedian position
  4. It consists of ascending and descending fibres connecting various cranial nerve nuclei (3, 4, 6 and 8).
  5. None of the above

Answer: 3. It is present throughout the brainstem in the same paramedian position

Question 7. Medial medullary syndrome is caused by to occlusion of

  1. Anterior spinal artery
  2. Posterior inferior cerebellar artery
  3. Pontine artery
  4. Vertebral artery

Answer: 1. Anterior spinal artery

Question 8. Lateral medullary syndrome is caused due to

  1. Occlusion of vertebral artery
  2. Anterior spinal artery
  3. Posterior inferior cerebellar artery
  4. Anterior inferior cerebellar artery

Answer: 3. Posterior inferior cerebellar artery

Question 9. Which of the following cranial nerve nuclei lie in the medulla?

  1. Facial nerve nucleus
  2. Abducent nerve nucleus
  3. Sensory nucleus of the trigeminal nerve
  4. The dorsal nucleus of the vagus

Answer: 4. Dorsal nucleus of the vagus

Question 10. The following sensations are carried by the tracts of the posterior spinal column (funiculus) except

  1. Proprioceptive sensation
  2. Tactile localisation
  3. Bladder distension
  4. Pain

Answer: 4. Pain

Question 11. Which is false regarding branches supplying blood to the medulla?

  1. Posterior inferior cerebellar artery
  2. Unnamed branches form vertebral arteries
  3. Posterior spinal artery
  4. Anterior inferior cerebellar artery
  5. Anterior spinal artery

Answer: 1. Posterior inferior cerebellar artery

Question 12. Which of the following statements about the connection of the medulla to the cerebellum is true?

  1. Through afferent fibres only
  2. Through both afferent and efferent fibres
  3. Through the middle cerebellar peduncle
  4. Through both middle and inferior cerebellar peduncles

Answer: 2. Through both afferent and efferent fibres

Brainstem Pons Multiple Choice Questions

Brainstem Pons Multiple Choice Questions

Question 1. Which of the following statements about pons is false?

  1. It lies in front of the cerebellum
  2. The posterior laulaco oi pons IN is formed by the upper surface of the Iho root of the fourth ventricle.
  3. The posterior surface of pons Is lit laterally by
    superior cerebellar peduncles
  4. The posterior surface of the pons Is released In the cerebellum

Answer: 2. The posterior laulaco oi pons IN is formed by the upper surface of the Iho root of the fourth ventricle.

Question 2. Which of the following statements about pons Is false?

  1. The ventral surface of pons Is bounded by upper and lower bonders
  2. The ventral surface of pons Is convex
  3. There is a shallow basilar groove In the midline, which lodges the basilar plexuses of veins
  4. Laterally, the ventral surface is continuous with the middle cerebellar peduncle
  5. The ventral surface of the pons is About the basisphenoid (clivus) bone

Answer: 3. Laterally, the ventral surface is continuous with the middle cerebellar peduncle

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Question 3. All the following statements about the transverse section of the pons are true except.

  1. The section is divided into basilar and tegmental parts
  2. The basilar part contains transversely and vertically running white fibres
  3. The basilar part does not contain grey matter (nuclei)
  4. Transverse fibres run laterally to form the middle cerebellar peduncle
  5. Vertical fibres run downwards to form the pyramid

Answer: 3. The basilar part does not contain grey matter (nuclei)

Question 4. Which of the following descending fibres are present in the die basilar part of die pons?

  1. Corticospinal
  2. Corticonuclear
  3. Corticopontine
  4. All of the above

Answer: 4. All of the above

Question 5. Which of the following statements about the corticomotor cerebellar pathway is false?

  1. It arises from frontal, temporal, parietal and occipital lobes
  2. It terminates on pontine nuclei of the same side
  3. The fibres arising from pontine nuclei constitute transverse fibres (pontocerebellar) of the pons
  4. Pontocerebellar fibres enter the cerebellum on the same side through the middle cerebellar peduncle.

Answer: 4. Pontocerebellar fibres enter the cerebellum on the same side through the middle cerebellar peduncle.

Question 6. The Efforts of the vestibular a relay Million In die 1 in 3 pilot cerebellar pathway of die vrullbiilm mu leur complex form die following?

  1. Vestibulocerebeller tract
  2. Vestibulospinal tract
  3. Medial longitudinal bundle
  4. lateral lemniscus
  5. Medial lemniscus

Answer: 5. Medial lemniscus

Question 7. The trapezoid body is formed by

  1. Fibre of both dorsal and ventral cochlear nuclei
  2. Efferents iirlulng from superior olivary nuclei
  3. Efferents arising from (lie nucleus of die trapezoid body
  4. All of the above

Answer: 4. All of the above

Question 8. Which of the following menisci are present in the white mailer of tegmentum at the upper level of pons?

  1. Medial lemniscus
  2. Spinal lemniscus
  3. Trigeminal lemniscus
  4. Lateral lemniscus
  5. All of the above

Answer: 5. All of the above

Question 9. The following statements about pontine haemorrhage are true except

  1. It occurs due to occlusion or haemorrhage of pontine arteries
  2. Corticospinal fibres are damaged leading to hemiplegia on the opposite side of the body
  3. Facial paralysis on the opposite side of the body due to damage to the facial nucleus
  4. There is hyperpyrexia due to damage to sympathetic fibres through which the heat-regulating centre exerts its effect
  5. Pinpoint pupil due to damage to sympathetic fibres

Answer: 3. Facial paralysis on the opposite side of the body due to damage to the facial nucleus

Question 10. Which ofthe following facts about Raymond’s syndrome are true?

  1. It results from to occlusion of pontine branches of the basilar artery
  2. Damage occurs to corticospinal fibres
  3. Damage to abducent nerve fibres
  4. All of the above

Answer: 4. All of the above

CBSE Notes For Class 6 Social Science Chapterwise

Geography

  • Chapter 1 The Earth In The Solar System Notes
  • Chapter 2 Globe: Latitudes and Longitudes Notes
  • Chapter 3 Motions of The Earth Notes
  • Chapter 4 Maps
  • Chapter 5 Major Domains of the Earth Notes
  • Chapter 6 Our Country- India Notes

Civics

  • Chapter 1 Understanding Diversity Notes
  • Chapter 2 Diversity and Discrimination Notes
  • Chapter 3 What is Government ? Notes
  • Chapter 4 Panchayati Raj Notes
  • Chapter 5 Rural Administration Notes
  • Chapter 6 Urban Administration Notes
  • Chapter 7 Rural Livelihoods Notes
  • Chapter 8 Urban Livelihoods Notes

History

CBSE Notes For Class 6 Science Chapterwise

CBSE Class 6 Science