CBSE Class 10 Science Chapter 2 Acids And Bases And Salts Short Answer Questions

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CBSE Class 10 Science Chapter 2 Acids And Bases And Salts

Salts:

CBSE Class 10 Science Chapter 2 Acids And Bases And Salts Common And Backinig Salt

Indicators:

CBSE Class 10 Science Chapter 2 Acids And Bases And Salts Indicators

CBSE Class 10 Science Chapter 2 Acids And Bases And Salts Definitions

1. Acids: Acids are sour and change the colour of blue litmus to red.

Examples of Acids:

Hydrochloric acid: HCI

Sulphuric acid: H2SO4

Nitric acid: HNO3

Acetic acid: CH3COOH

Phosphoric acid: H3PO4

Read and Learn More CBSE Class 10 Science Short Answer Questions

2. Properties of an Acidic Solution:

  1. Tastes sour.
  2. Reacts with metals such as zinc, magnesium, etc. liberating hydrogen gas.
  3. Changes the colour of litmus from blue to red.
  4. Conducts electricity.

3. Bases: Bases are bitter and change the colour of red litmus to blue

Examples of Bases:

Sodium hydroxide: NaOH

Potassium hydroxide: KOH

Ammonium hydroxide: NH4OH

Calcium hydroxide : Ca(OH)2

Barium hydroxide : Ba(OH)2

4. Properties of a Basic Solution:

  1. Tastes bitter, and feels slippery.
  2. Reacts with an acidic solution to neutralize the properties or characteristics of an acid.
  3. Changes the colour of litmus from red to blue.
  4. Conducts electricity.

5. Indicators:

Indicators are chemical substances which give different colours in acidic or basic solutions.

6. Olfactory indicators:

The substances which have different odours in acid and base solution. For example, vanilla essence has a characteristic pleasant-smelling acid solution and no smell in an alkali solution.

7. Reaction of acids with metals:

Acid + Metal→ Salt + Hydrogen gas

H2SO4(aq) + Zn(s)→ ZnSO4(aq) + H2(g)

8. Reaction of bases with metals:

Base + Metal→ Salt + Hydrogen

2NaOH + Zn→ Na2ZnO2+ H2

9. Reaction of Acids with metal Carbonates:

Acid + Metal Carbonate→ Salt + CO2 + H2O

2HCl(aq) + Na2CO3(s)→2NaCl(aq) + CO2(g) + H2O(Z)

10. Reaction of Acids with metal Hydrogen Carbonates:

Acid + Metal Hydrogen Carbonate→ Salt + CO2 + H2O

HCl(aq) + NaHCOg(s) NaCl (aq) + CO2(aq) + H2O(l)

11. Neutralization reaction:

When the effect of a base is nullified by an acid and vice-versa is called a neutralization reaction.

Base + acid→ Salt + water

NaOH + HCl→ NaCl + H2O

12. Antacids:

Antacids are mild alkalies and contain sodium hydrogen carbonate. These are used for getting relief from acidity and indigestion and sometimes, even headaches.

13. Reaction of Acids with metallic Oxides:

Acid + Metal Oxides → Salt + Water

2HCl(aq) + CuO(s)

CuCl2(aq) + H2O(l)

14. All acids generate H+ ions and all bases generate OH– ions in the presence of water and this helps acids and bases to conduct electricity.

15. Universal indicators:

An indicator which passes through a series of colour changes over a wide range of H3O+ (hydronium) ion concentrations is called a universal indicator. It is a mixture of several indicators.

16. pH: pH is a number which indicates the acidic or basic nature of a solution.

17. pH scale: pH scale is the scale for measuring hydrogen ion or hydronium ion concentration in a solution.

pH =- log [H3O+]

18. Acid rain: When the pH ofrain water is less than 5-6, is called acid rain.

19. Dilute acid: A dilute acid solution containing only a small amount of acid and a large amount of water.

20. Concentrated acid: A concentrated acid contains a large amount of acid and a small amount of water.

21. Salts: Salts are formed by the combination of acids and bases

Examples of Salts:

Sodium chloride: NaCl

Sodium carbonate: Na2CO3

Sodium hydrogen carbonate: NaHCO3

Ammonium nitrate: NH4NO3

Potassium sulphate: NH4NO3

22. Properties of a Salt Solution:

  1. Tastes salty.
  2. The colour of the litmus solution usually does not change when added to a salt solution. However, some salts turn blue litmus red whereas others turn red litmus blue.
  3. Conducts electricity.

23. Alkali: The hydroxide of metals which dissolve in water are known as alkalies.

24. Normal salt: It does not hydrolyse in water.

25. Acidic salt: It hydrolyses in water to give strong acids like H2SO4.

26. Basic salt: It hydrolyses in water to give a strong base like NaOH.

27. Water of crystallization: Water of crystallization is the fixed number of water molecules present in one formula unit of salt.

For example: CuSO4.5H2O, Na2CO3.10H2O.

28. Deliquescence: A substance that absorbs moisture gradually from the air is called a deliquescent substance and this phenomenon is called deliquescence.

29. Carbonation: It is a process in which brine (NaCl) saturated with ammonia is allowed to come in contact with carbon dioxide under pressure to form sodium bicarbonate.

30. Antichlor: Antichlor is a substance used to remove excess chlorine from material or cloth.

For example sodium bisulphite, and sodium thiosulphate.

31. Hydrolysis: The interaction of a salt with water to give an acid and base is called salt hydrolysis.

32. Hydrated salts: Some salts crystallize with a fixed number ofwater molecules attached to one formula unit of salt.

33. Common Salt- Sodium Chloride (NaCl)

NaOH + HCl→ NaCl + H2O

34. Caustic soda- Sodium hydroxide (NaOH)

2 NaCl(aq) +2H2O(l) → Electricity  → 2NaOH (aq) +Cl(g)+H(g)

35. Bleaching Powder- Calcium Oxychloride (CaOCl2)

Ca(OH)2 + Cl2 → CaOCl2 + H2O

36. Baking Soda- Sodium hydrogen Carbonate (NaHCO3)

NaCl + NH3 + CO2 + H2O → NaHCO3 + NH4Cl

37. Washing Soda- Sodium Carbonate decahydrate  → Na2CO3.10H2O

38. Plaster of Paris: CaSO4. H2O is known as Plaster of Paris when wetted with water sets to a hard porous mass within 10-15 minutes

CBSE Class 10 Science Chapter 2 Acids And Bases And Salts Short Question And Answers

Question 1. Five solutions A, B, C, D and E when tested with a universal indicator showed pH of 4, 1,11,7 and 9, respectively. Which solution is it?

  1. Neutral
  2. Strongly alkaline
  3. Strongly acidic?
  4. Weakly alkaline?

Arrange the pH in increasing order of hydrogen-ion concentration.
Answer:

  1. D
  2. C
  3. B
  4. A
  5. E

11<9<7<4<1

Question 2. Equal lengths of magnesium ribbons are taken in test tubes A and B. Hydrochloric acid (HCl) is added to test tube A, while acetic acid (CH3COOH) is added to test tube B. The amount and concentration taken for both acids are the same. In which test tube will the fizzing occur more vigorously and why?
Answer:

Fizzing will occur more vigorously in test tube A containing hydrochloric acid. This is because hydrochloric acid is stronger than acetic acid and gives more H+ ions quickly.

Thus, the reaction between magnesium ribbon and HCl is faster than between Mg and acetic acid.

Question 3. A milkman adds a very small amount of baking soda to fresh milk.

  1. Why does he shift the pH ofthe fresh milk from 6 to slightly alkaline?
  2. Why does this milk take a long time to set as curd?

Answer:

  1. The milkman adds a little baking soda to fresh milk to make it slightly alkaline so that it can be preserved for a longer time.
  2. Initially, lactic acid formed is used up to neutralize the base and when more lactic acid is formed, the milk sets as curd.

Question 4. Give two important uses of washing soda and baking soda.
Answer:

Uses of baking soda:

  1. It is used in bakery.
  2. It is used in soda acid fire extinguishers.

Uses of washing soda:

  1. It is used in the manufacture of glass, soap and paper.
  2. It is used for removing the permanent hardness of water

Question 5. You have been provided with three test tubes. One of them contains distilled water and the other two contain an acidic solution and a basic solution, respectively. If you are given only red litmus paper, how will you identify the contents ofeach test tube?
Answer:

  1. Dip red litmus paper separately in three test tubes.
  2. The test tube in which red litmus turns blue contains the basic solution. Now dip the blue litmus in the other two test tubes.
  3. The tube which turns blue litmus red contains the acid solution. The tube in which litmus paper gives a purple colour contains distilled water.

Question 6. Why should curd and sour substances not be kept in brass and copper vessels?
Answer:

  1. Curd and sour substances contain acids which react with brass and copper vessels.
  2. Thus, brass and copper vessels get corroded.
  3. Further, the products formed make the food unfit for eating.

Question 7. Metal compound A reacts with dilute hydrochloric acid to produce effervescence. The gas evolved extinguishes a burning candle. Write a balanced chemical equation for the reaction if one of the compounds formed is calcium chloride
Answer:

Since the end product is calcium chloride and the gas formed extinguishes a burning candle, it is CO2 and metal compound A must be calcium carbonate. Hence, the balanced chemical equation for the reaction is as below

CaCO3+ 2HCl→CaCl + CO2 + H2O

Question 8. Why do HCl, HNO3, etc., show acidic characteristics in aqueous solutions while solutions of compounds like alcohol and glucose do not show acidic characteristics?
Answer:

Compounds like HCl, HNO3, etc. release H+ ions in aqueous solution and hence show acidic character while alcohol and glucose do not release H+ ions in aqueous solution, and hence do not show acidic character.

Question 9. While diluting an acid, why is it recommended that the acid should be added to water and not water to the acid?
Answer:

When water is added to acid, there is a sudden rise in temperature with explosion and the acid being present in bulk, it gets spilt on your body and clothes.

When an acid is added to water, the water is in bulk and the acid being heavier settles down and the heat evolved is dissipated in the water itself hence, the spurting of the liquid is minimised. For this reason, it is recommended that acid should be added to water in small amounts with stirring to dilute the concentrated acid.

Question 10. What will happen if a solution ofsodium hydrocarbonate is heated1? Give the equation of the reaction involved.
Answer:

Sodium hydrogen carbonate solution on heating gives sodium carbonate, water with evolution of carbon dioxide gas.

2 NaHCO3(aq) → (Heat) → Na3CO2(s)+H2O(l)+CO2(g)

Question 11. Write an equation to show the reaction between Plaster of Paris and water.
Answer:

The reaction between Plaster of Paris and water:

⇒ \(\underset{\text { Plaster of Paris }}{2 \mathrm{CaSO}_4 \cdot \frac{1}{2} \mathrm{H}_2 \mathrm{O}}+\mathrm{H}_2 \mathrm{O} \longrightarrow \underset{\text { Gypsum }}{2 \mathrm{CaSO}_4 \cdot 2 \mathrm{H}_2 \mathrm{O}}\)

Question 12. Crystals of copper sulphate are heated in a test tube for some time

1. What is the colour of copper sulphate crystals

  1. Before heating, and
  2. After heating?

2. What is the source of liquid droplets? Seen on the inner upper side of the test tube during the heating process?

Answer:

1. 

  1. Blue
  2. White

2. Crystals of copper sulphate (CuSO4.5H2O) contain water of crystallisation and on heating these crystals lose water and become white. This lost water can be seen in the form of droplets on the inner upper side ofthe test tube.

Question 13. Effervescence arc formed when the batter for cake is heated. Which substance is present in the batter? Name the gas evolved. Write the chemical equation involved.
Answer:

The substance present is baking soda (NaHCO3).

The gas evolved in CO

2NaHCO3 → (Heat)→ Na2CO3 + H2O + CO

Question 14. State the number of water molecules present in crystals of washing soda and Plaster of Paris. What are these water molecules called?
Answer:

1. Washing soda: 10 molecules of water.

Plaster of Paris: 1/2 molecule of water.

2. These molecules are called water of crystallisation.

Question 15. Acids do not show acidic behaviour in the absence of water but do so in water. Justify this statement with the help ofa chemical equation.
Answer:

Acids ionise in aqueous medium to form hydrogen ions. These hydrogen ions cannot exist alone, they exist after combining with water molecules. Thus, aqueous hydrogenions which are responsible for acidic behaviour can exist in the presence of water only.

H+(Hydrogen ion)+H2O(water) + H3O+ (Hydronium ion)

These hydrogen ions are as shown as H+(aq) or hydronium ions (H2O+).

Question 16. Give three practical applications of a neutralisation reaction.
Answer:

  • Antacids have been developed based on neutralisation reactions.
  • Toothpaste is basic which neutralises the excess of acid produced in our mouth.
  • Milkman adds a very small amount of baking soda to milk to neutralise the lactic acid produced in the milk.

Question 17.

  1. Define olfactory indicators. Name two substances which can be used as olfactory indicators.
  2. Choose strong acids from the following:
  3. CH3COOH, H2SO4, H2CO3, HNO3

Answer:

1. Those substances whose smell (odour) changes in acidic or basic solution are called olfactory indicators,

Example: Onion and vanilla.

2. H2SO4 and HNO3 are strong acids.

Question 18. 15 mL of water and 10 mL of sulphuric acid are to be mixed in a beaker.

  1. State the method that should be followed with reason.
  2. What is this process called?

Answer:

  1. The acid is to be added slowly in water to prevent the mixture to be splashed. The reaction is highly exothermic, therefore, constant cooling should be done.
  2. The process is called dilution.

Question 19. The marble statues are often slowly corroded when kept in open for a long time. Give a suitable reason.
Answer:

Chemically, marble is calcium carbonate. All metal carbonates and hydrogen carbonates react with acids to give corresponding salt, carbon dioxide and water.

Calcium carbonate reacts with acids to form calcium hydrogen carbonate, which is soluble in water and thus washed away. So the marble statues are slowly corroded.

CaCO3(s) + H2O(l) + CO2(g) → Ca(HCO3)2(aq)

Question 20.

  1. State the purpose of developing scale.
  2. Mention the pH range for acids.
  3. What is the pH of acid rain and how it affects aquatic life?

Answer:

  1. The purpose of developing a pH scale was to quantify the amount of H+ or OH– ions in a solution.
  2. The pH range for acids is 0 -7.
  3. When the pH ofrain water is less than 5.6, it is called acid rain. It lowers the pH of river water. Thus, the survival of aquatic life becomes difficult.

Question 21. Deepika prepares HCl gas in her school laboratory using certain chemicals. She puts both dry and wet blue litmus papers in contact with the gas.

  1. Name the reagents used by Deepika to prepare HCl gas.
  2. State the colour changes observed with the dry and wet blue litmus paper.
  3. Show the formation of ions when HCl gas combines with water.

Answer:

The reagents used by Deepika to prepare HCl gas are sodium chloride and sulphuric acid.

There is no colour change observed with dry litmus paper. However, wet blue litmus paper turns red.

HCI + H2O → H3O+ + Cl–

Question 22.

  1. If we take hydrochloric acid and acetic acid of the same concentration, which one will produce less H+ ion concentration? Out of two, which one is a weak acid?
  2. If someone is suffering from acidity, which ofthe following would you suggest to cure it: Vinegar, orange juice, or baking soda solution? Give reasons for your cone.

Answer:

1.

  1. Out of hydrochloric acid and acetic acid of the same concentration, acetic acid will produce fewer H+ ions.
  2. Acetic acid is weaker than hydrochloric acid.

2. If someone is suffering from acidity,I would suggest baking soda solution to cure it because it neutralises the excess acid produced in the stomach and provides relief.

Question 23. Write the chemical name and formula of the following:

  1. Salt is formed by the combination of weak acids like carbonic acid and strong bases like sodium hydroxide.
  2. Basic substance formed by the chlor-alkali process.
  3. Substances are added in cakes to make them fluffy.

Answer:

  1. Sodium carbonate (Na2CO3).
  2. Sodium hydroxide (NaOH).
  3. Sodium hydrogen carbonate (NaHCO3).

Question 24.

  1. Name the products obtained in the chlor-alkali process.
  2. Name the gases liberated at the anode and at the cathode respectively.
  3. Name the solution which is used as raw material in this process.

Answer:

  1. Chlorine gas, hydrogen gas and sodium hydroxide solution.
  2. Chlorine gas is given off at the anode and hydrogen gas at the cathode.
  3. Brine solution

Question 25. Explain why

  1. The colour of copper sulphate crystals changes on heating.
  2. Baking soda acts as an antacid.
  3. An acid should be added to water while diluting. 

Answer:

  1. It loses its 5 molecules of water of crystallisation, hence colour changes.
  2. It is alkaline and neutralises excess acid to relieve pain.
  3. As dilution of acids is an exothermic reaction and adding water to acids will splash and cause burns

Question 26.

1. Give the chemical names of acids present in

  1. Ant
  2. Lemon
  3. Milk
  4. Tomato

2. Write the chemical names of two salts belonging to the sodium family

Answer:

1.

  1. Formic acid/methanoic acid
  2. Citric acid
  3. Lactic acid
  4. Oxalic acid

2.

  1. Soddiumcarbonate (Na2CO3)
  2. Sodium sulphate (Na2SO4)

Question 27.

  1. What do you understand by the term hydrated salt?
  2. Give two examples of hydrated salt which are white and state their chemical formula.

Answer:

1. The salts having water of crystallisation with them are known as hydrated salts. Some salts unite with a definite quantity of water while crystallising out from their solutions, and this is known as the water of crystallisation.

2.

  1. Sodium sulphate decahydrate (Na2CO3.10H2O). It is commonly known as washing soda.
  2. Hydrated calcium sulphate (CaSO4.2H2O). It is commonly known as gypsum.

Question 28. Given below are the pH values of our different liquids: 7.0, 14.0, 4.0, 2.0, Which of these could be that of

  1. Lemon juice
  2. Distilled water
  3. 1 M sodium hydroxide solution
  4. Tomato juice

Answer:

1. Lemon juice pH = 2.0

2. Distilled water pH = 7.0

3. 1 M NaOH pH = 14.0

4. Tomato juice pH = 4.0

Question 29.

  1. Write the name given to bases that are highly soluble in water. Give an example.
  2. How is tooth decay related to pH? How can it be prevented?
  3. Why does a bee sting cause pain and irritation? Rubbing baking soda on the sting area gives relief. How?

Answer:

  1. Alkali Example: NaOH (Sodium hydroxide)
  2. The lower the pH, the more will be tooth decay. Acid reacts with Ca3(P04)2 and causes tooth decay. It can be prevented by brushing our teeth after every meal.
  3. It is due to formic acid. Sodium hydrogen carbonate (Baking soda) neutralises formic acid giving relief.

Question 30. “Sodium hydrogen carbonate is a basic salt”. Justify the statement. How is it converted into washing soda? Explain.
Answer:

Sodium hydrogen carbonate is a salt of sodium hydroxide (strong base) and carbonic acid (weak acid).

It is a basic salt. It is converted into washing soda by heating followed by crystallisation

2 NaHCO3 →  (Heat) → Na2CO3 + CO2 +H2O

Question 31. A white powder is added while baking bread and cakes to make them soft and fluffy. Write the name of the powder. Name its main ingredients. Explain the function ofeach ingredient. Write the chemical reaction taking place when the powder is heated during baking.
Answer:

Baking powder.

It consists of sodium hydrogen carbonate and tartaric acid. Sodium hydrogen carbonate gives CO2 which makes cake soft and fluffy. Tartaric acid neutralises the bitterness due to the sodium carbonate produced.

2NaHCO3(s)→  (Heat) → Na2CO3(s) +CO2(g) +H2O(l)

Question 32. Classify the following salts into acidic, basic and neutral: Potassium, sulphate, ammonium chloride, sodium carbonate, sodium chloride.
Answer:

Neutral: Potassium sulphate, Sodium chloride

Acidic: Ammonium chloride

Basic: Sodium carbonate

Question 33.

  1. Name the compound which is obtained from baking soda and is used to
    permanent hardness of water.
  2. Write its chemical formula.
  3. What happens when it is recrystallised from its aqueous solution?

Answer:

  1. Sodium carbonate is obtained from baking soda and is used to remove the hardness of water.
  2. Na2CO3.
  3. It changes to washing soda, Na2CO3.10H2O

Question 34. Tooth enamel is one ofthe hardest substances in our body. How does it undergo damage due to eating chocolates and sweets? How does toothpaste prevent this damage?
Answer:

Tooth enamel is made up of calcium phosphate. Chocolates and sweets produce acid in our mouth which reacts with enamel (calcium phosphate) and leads to cavities. We should brush our teeth after every meal as well as after eating sweets, etc.

Question 35.

  1. What is a universal indicator?
  2. Write the chemical equation involved in the preparation ofsodium hydroxide. Name the process.

Answer:

1. Universal is a mixture of synthetic Indicators which is used to find pH of solutions,

2. 2NaCl(aq) + 2H2O(Z)→  (Electrolysis)→ 2NaOH(aq)+ H2(g) + Cl2(g)

It is called the chlor-alkali process.

Question 36. What happens when chlorine is passed over slaked lime at 313K? Write the chemical equation of the reaction involved and state two uses ofthe product obtained.
Answer:

Bleaching powder is formed

Ca(OH)2(s) +Cl2(g) → (313 K) → CaOCl2(s)+H2O(l)

Bleaching powder Uses:

  1. It is used as a bleaching agent in paper and textile industries.
  2. It is used as a disinfectant in the purification of drinking water.

Question 37. Name the acid present in an ant sting andgive its chemical formula. Also, give a common method to get relief from the discomfort caused by the ant sting.
Answer:

The acid present in ant sting is methanoic acid (formic acid). The chemical formula is HCOOH. To get relief one should apply any available basic salt

Example: Baking soda (NaHCO3) on it.

Question 38. What happens when nitric acid is added to the shell?
Answer:

Eggshell contains CaCO3. When nitric acid is added to it, the following reaction takes place with the evolution of CO2

CaCO3 + 2 HNO3 → Ca(NO3)2 + H2O + CO2

As a result, the shell slowly dissolves in nitric acid.

Question 39. A student prepared solutions of

  1. An acid and
  2. A base in two separate beakers.

She forgot to label the solutions and litmus paper is not available in the laboratory. Since both the solutions are colourless, how will she distinguish between the two?
Answer:

If litmus paper is not available, phenolphthalein and methyl orange can be used.

Take a few drops of the two solutions in two separate test tubes. Add 1-2 drops of phenolphthalein in each of them. The solution which turns phenolphthalein pink is a base.

The other solution (acidic) will remain colourless. Clean the test tubes and repeat the experiment with methyl orange. The solution which turns methyl orange red is an acid. The colour in the other (basic) solution will be yellow.

Question 40. Salt A commonly used in bakery products on heating gets converted into another salt B which itself is used for the removal of the hardness of water and a gas C is evolved. The gas C when passed through lime water, turns it milky. Identify A, B, and C. Heat
Answer:

CBSE Class 10 Science Chapter 2 Acids And Bases And Salts Backing Powder

So A = NaHCO3

B = Na2CO3

C = CO2

Question 41. What are strong and weak acids? In the following list of acids, separate strong acids from weak acids. Hydrochloric acid, citric acid, acetic acid, nitric acid, formic acid, sulphuric acid.
Answer:

In aqueous solutions, strong acids ionise completely and provide hydronium ions. On the other hand, weak acids are partially ionised and an aqueous solution of the same molar concentration provides a much smaller concentration of H3O+ ions.

  1. Strong acids—Hydrochloric acid, sulphuric acid, nitric acid
  2. Weak acids—Citric acid, acetic acid, formic acid

Question 42. When zinc metal is treated with a dilute solution ofa strong acid, a gas is evolved, which is utilisedin the hydrogenation of oil. Name the gas evolved. Write the chemical equation ofthe reaction involved and also write a test to detect the gas formed.
Answer:

When zinc reacts with a dilute solution of strong acid, it forms salt and hydrogen gas is evolved.

Zn + 2HCl→  ZnCl2 + H2

When a burning splinter is brought near the mouth ofthe test tube, the gas burns with a pop sound.

Question 43. Kiran was suffering from toothache. She never brushed her teeth before sleeping at night.

  1. She loves to eat chocolates and ice cream.
  2. What is, in general, the cause of toothache?
  3. What our teeth are made up of?
  4. How does toothpaste help in preventing toothache?

Answer:

  1. Tooth decay starts when pH of the mouth is lower than 5.5. The acid so produced attacks the teeth and produces cavities which cause pain.
  2. Calcium phosphate.
  3. Toothpaste is generally basic, thus it helps in neutralising acids.

Question 44. Karan’s mother had severe pain when a honeybee stung her hand. Karan’s granny tried to relieve the pain by rubbing a metal on the stung area. But Karan picked up the baking powder from the kitchen and applied it on her mother’s hand which quickly relieved the pain.

  1. Why does honeybee stinging cause pain?
  2. How does baking powder relieve the bee-sting pain?
  3. What value of Karan is seen in the above case?

Answer:

  1. Honeybee sting consists of acid that is released in our body and causes pain.
  2. Baking powder is basic, it neutralises the acid released in our body by bee-sting and relieves the pain.
  3. Karan showed the value of prompt, proactive and responsible behaviour.

Question 45. Pooja’s friend is very fond, of coffee. He drinks a cup of coffee every day before he goes to school and faces the problem of stomachache very often. Pooja advised him not to drink coffee in the morning.

  1. What was the cause of stomachache?
  2. What would be the pH of stomach juices after consuming coffee?
  3. What values of Pooja are reflected in the above act?

Answer:

  1. A cup of coffee causes acidity that leads to stomachache.
  2. The pH of the stomach after drinking coffee is 5.
  3. Pooja showed the value of concern, caring and awareness.

Question 46. Substance A, an oxide of group 2 elements, is used intensively in the cement industry. This element is present in bones also. On treatment with water, it forms a solution which turns red litmus blue. Identify A’ and also write the chemical reaction involved.
Answer:

A is calcium and chemical reaction involved:

CaO(s) + H2O(Z) → (Basic solution)Ca(OH)2(aq)

Question 47. What happens when the shell is placed in concentrated nitric acid in a beaker?
Answer:

Evolution of CO2 occurs and the shell dissolves slowly

⇒ \(\mathrm{CaCO}_3+2 \mathrm{HNO}_3(\text { Conc. }) \longrightarrow \mathrm{Ca}\left(\mathrm{NO}_3\right)_2+\mathrm{H}_2 \mathrm{O}+\mathrm{CO}_2(\uparrow)\)

Question 48. In one ofthe industrial processes used for the manufacture of NaOH, a gas X’ is formed as a by-product. The gas ‘X reacts with lime water to give a compound which is used as a bleaching agent in the chemical industry. Identify X’ and IT.
Answer:

X = Cl2 and Y = CaOCl2

⇒ \(\mathrm{Ca}(\mathrm{OH})_2+\underset{[\mathrm{X}]}{\mathrm{Cl}_2} \longrightarrow \underset{[\mathrm{Y}]}{\mathrm{CaOCl}_2}+\mathrm{H}_2 \mathrm{O}\)

CBSE Class 10 Science Chapter 2 Acids And Bases And Salts Multiple Choice Questions

Question 1. What happens when a solution of an acid is mixed with a tube?

1. The temperature ofthe solution increases

2. The temperature ofthe. solution decreases

3. The temperature ofthe solution remains the

4. Salt formation takes place

  1. 1only
  2. 1 and 3
  3. 2 and 3
  4. 1 and 4

Answer: 4.1 and 4

Question 2. An aqueous solution turns red litmus solution blue. Excess addition of which of the following solutions would reverse the change? solution of a base in a test same

  1. Baking powder
  2. Lime
  3. Ammonium hydroxide solution
  4. Hydrochloric acid

Answer: 4. Hydrochloric acid

Question 3. During the preparation of hydrogen chloride gas on a humid day, the gas is usually passed through the guard tube containing calcium chloride. The role of calcium chloride taken in the guard tube is to

  1. Absorb the evolved gas
  2. Moisten the gas
  3. Absorb moisture from the gas
  4. Absorb Cl– ions from the evolved gas

Answer: 3.  Absorb moisture from the gas

Question 4. Which ofthe following salts does not contain water of crystallisation?

  1. Blue vitriol
  2. Baking soda
  3. Washing soda
  4. Gypsum

Answer:  2. Baking soda

Question 5. Sodium carbonate is a basic salt because it is a salt of

  1. Strong acid and strong base
  2. Weak acid and weak base
  3. Strong acid and weak base
  4. Weak acid and strong base

Answer: 4. Weak acid and strong base

Question 6. Calcium phosphate is present in tooth enamel. Its nature is

  1. Basic
  2. Acidic
  3. Neutral
  4. Amphoteric

Answer: 1.  Basic

Question 7. A sample of soil is mixed with water and allowed to settle. The clear supernatant solution turns the pH paper yellowish-orange. Which of the following would change the colour of the paper to greenish-blue?

  1. Lemon juice
  2. Vinegar
  3. Common salt
  4. An antacid

Answer: 4. An antacid

Question 8. Which of the following gives the correct increasing order of acidic strength?

  1. Water < Acetic acid < Hydrochloric acid
  2. Water < Hydrochloric acid < Acetic acid
  3. Acetic acid < Water < Hydrochloric acid
  4. Hydrochloric acid < Water < Acetic acid

Answer: 1.  Water < Acetic acid < Hydrochloric acid

Question 9. If should a few be dropped of? a concentrated acid accidentally spills over the hand ofa student, what should be done?

  1. Wash the hand with saline solution
  2. Wash the hand immediately with plenty of water and apply a paste ofsodium hydrogen carbonate
  3. After washing with plenty of water, apply a solution of sodium hydroxide to the hand
  4. Neutralise the acid with a strong alkali

Answer: 2.  Wash your hand immediately with plenty of water and apply a paste ofsodium hydrogen carbonate

Question 10. Sodium hydrogen carbonate when added to acetic acid evolves a gas. Which of the following statements are true about the gas evolved?

1. It turns lime water milky

2. It extinguishes a burning splinter

3. It dissolves in a solution ofsodium hydroxide

4. It has a pungent odour

  1. 1 and 2
  2. 1, 2 and 3
  3. 2, 3 and 4
  4. 1 and 4

2.  1, 2 and 3

Question 11. Common salt besides being used in the kitchen can also be used as the raw material for making

1. Washing soda

2. Bleaching powder

3. Baking soda

4. Slaked lime

  1. 1 and 3
  2. 2 and 3
  3. 1 and 4
  4. 2 and 4

Answer: 3.  1 and 4

Question 12. One of the constituents of baking powder is sodium hydrogen carbonate, the other constituent is

  1. Hydrochloric acid
  2. Tartaric acid
  3. A cetic acid
  4. Sulphuric acid

Answer:  2. Tartaric acid

Question 13. To protect from tooth decay we are advised to brush our teeth regularly. The nature of the toothpaste commonly used is

  1. Acidic
  2. Neutral
  3. Basic
  4. Corrosive

Answer: 3. Basic

Question 14. Which ofthe following statements is correct about an aqueous solution of an acid and of a base?

1. The higher the pH, the stronger the acid

2. The higher the pH, the weaker the acid

3. The lower the pH, the stronger the base

4. The lower the pH, the weaker the base

  1. 1 and 3
  2. 2 and 3
  3. 1 and 4
  4. 2 and 4

Answer: 4. 2 and 4

Question 15. The pH of the gastric juices released during digestion is

  1. Less than 7
  2. More than 7
  3. Equal to 7
  4. Equal to 0

Answer: 1. Less than 7

Question 16. Which ofthe following phenomena occur, when a small amount of acid is added to water?

1. Ionisation

2. Neutralisation

3. Dilution

4. Salt formation

  1. 1 and 2
  2. 1 and 3
  3. 2 and 3
  4. 2 and 4

Answer:  2. 1 and 3

Question 17. Which one ofthe following can be used as an acid-base indicator by a visually impaired student?

  1. Litmus
  2. Turmeric
  3. Vanilla essence
  4. PetuniaI leaves

Answer: 3. Vanilla essence

Question 18. Which of the following substances will not give carbon dioxide on treatment with dilute acid?

  1. Marble
  2. Limestone
  3. Baking soda
  4. Lime

Answer: 4. Lime

Question 19. Which ofthe following is acidic?

  1. Lime juice
  2. Human blood
  3. Lime water
  4. Antacid

Answer: 1.  Lime juice

Question 20. In an attempt to demonstrate electrical conductivity through an electrolyte, the following apparatus was set up.

1. Which among the following statement(s) is(are) correct?

2. The bulb will not glow because the electrolyte is not acidic

3. The bulb will glow because NaOH is a strong base and furnishes ions for conduction

4. The bulb will not glow because the circuit is incomplete

The bulb will not glow because it depends upon the type of electrolytic solution

  1. 1 and 3
  2. 2 and 4
  3. 2 only
  4. 4 only

Answer: 3. 2 only

Question 21. Which ofthe following is used for the dissolution of gold?

  1. Hydrochloric acid
  2. Sulphuric acid
  3. Nitric acid
  4. Aqua regia

Answer: 4.  Aqua regia

Question 22. Which of the following is not a mineral acid?

  1. Hydrochloric acid
  2. Citic acid
  3. Sulphuric acid
  4. Nitric acid

Answer: 2. Citic acid

Question 23. Which among the following is not a base?

  1. NaOH
  2. KOH
  3. NH4OH
  4. C2H5OH

Answer: 4.  C2H5OH

Question 24. Which ofthe following statements is not correct?

  1. All metal carbonates react with acid to give a salt, water and carbon
    dioxide
  2. All metal oxides react with water to give salt and acid
  3. Some metals react with acids to give salt and hydrogen
  4. Some non-metal oxides react with water to form an acid

Answer: 2.  All metal oxides react with water to give salt and acid

Question 25. Match the chemical substances given in Column (A) with their appropriate application given in Column (B)

CBSE Class 10 Science Chapter 2 Acids And Bases And Salts Match The Column Of Chemical Substances

  1. 1-B,2-A,3-D,4-C
  2. 1-C,2-B,3-D,4-A
  3. 1-C,2-D,3-1,4-2
  4. 1-B,2-D,3-A,4-C

Answer: 3.  1-C,2-D,3-1,4-2

Question 26. Equal volumes of hydrochloric acid and sodium hydroxide solutions of the same concentration are mixed and the pH of the resulting solution is checked with pH paper. What would be the colour obtained? (You may use the colour guide given below.)

CBSE Class 10 Science Chapter 2 Acids And Bases And Salts Hydrochloric Acid And Sodium Hydroxide Solution

  1. Red
  2. Yellowish-orange
  3. Yellowish green
  4. Blue

Answer: 3. Yellowish green

Question 27. Which ofthe following is(are) true when HCl(g) is passed through water?

1. It does not ionise in the solution as it is a covalent compound.

2. It ionises in the solution

3. It gives both hydrogen and hydroxyl ions in the solution

4. It forms hydronium ions in the solution due to the combination of hydrogen ions with a water molecule

  1. 1 only
  2. 3 only
  3. 2 and 4
  4. 3 and 4

Answer: 3. 2 and 4

Question 28. Which of the following statements is true for acids’?

  1. Bitter and change red litmus to blue
  2. Sour and change red litmus to blue
  3. Sour and change blue litmus to red
  4. Bitter and change blue litmus to red

Answer: 3. Sour and change blue litmus to red

Question 29. Which ofthe following are present in a dilute aqueous solution of hydrochloric acid?

  1. H3O++ Cl–
  2. H3O++ OH–
  3. Cl– + OH–
  4. Unionised HCl

Answer: 1. H3O++ Cl–

Question 30. Identify the correct representation ofreaction occurring during the chlor-alkali process

  1. 2NaCl(l) + 2H2O(l) → 2NaOH(Z) + Cl2(g) + H2(g)
  2. 2NaCl(aq) + 2H2O(aq)→  2NaOH(aq) + Cl2(g) + H2(g)
  3. 2NaCl(aq) + 2H2O(l) → 2NaOH(ag) + Cl2(aq) + H2(aq)
  4. 2NaCl(aq) + 2H(l) → 2NaOH(aq) + Cl2(g) + H2(g)

Answer: 4.  2NaCl(aq) + 2H2O(l) → 2NaOH(ag) + Cl2(aq) + H2(aq)

Question 31. Match the given in Column (A) with the correct source given in Column (B)

CBSE Class 10 Science Chapter 2 Acids And Bases And Salts Match Acids Given

Answer: 1-D ,2-C ,3- B ,4-A

Question 32. Match the important chemicals given in Column (A) with the chemical formulae given in Column (B)

CBSE Class 10 Science Chapter 2 Acids And Bases And Salts Important Chemicals

Answer: 1- B, 2-C, 3- D,4- A

Question 33. A solution turns red litmus blue. ItspH is likely to be

  1. 1
  2. 4
  3. 5
  4. 10

Answer: 4. 10

Question 34. A solution reacts with crushed eggshells to give a gas that turns lime-water milky. The solution contains

  1. NaCl
  2. HCl
  3. LiCl
  4. KCl

Answer: 4. KCl

Question 35. 10 mL ofa solution of NaOH is found to be completely neutralised by 8 mL of a given solution of HCl. If we take 20 mL of the same solution of NaOH, the amount of HCl solution (the same solution as before) required to neutralise it will be

  1. 4 mL
  2. 8 mL
  3. 12 mL
  4. 16 mL

Answer: 4. 16 mL

Question 36. Which one ofthe following types of medicines is used for treating indigestion?

  1. Antibiotic
  2. Analgesic
  3. Antacid
  4. Antiseptic

Answer: 3. Antacid

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