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

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

Question 1. Name an acid-base indicator prepared at home.
Answer: Beetroot extract.

Question 2. What is aqua regia?
Answer: It is a mixture of Cone HC1 and Cone. HN03 in the ratio of 3: 1.

Question 3. What will happen to blue litmus when it is added to soda water?
Answer: It changes to red.

Question 4. Which acid and base are used in the formation of the following salts?

1. CuSO₄
2. NaNO₃

Answer:

1. Cu(OH)₂ and H₂SO₄
2. NaOH and HNO₃

Question 5. What are antacids? Explain their role in providing relief from stomachache.
Answer:

1. Antacids are mild bases.
2. Antacids neutralize the effect of extra acid produced in the stomach during indigestion and thus provide relief.

Question 6. Define indicators. Name two natural indicators obtained from plants.
Answer: Indicators are substances which give different colours in acidic or basic solutions. Natural indicators from plants are litmus and Vanilla extract.

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Question 7. Make a distinction between metals and non-metals concerning the nature of their oxides.
Answer: Metal gives basic oxides and non-metal gives acidic oxides.

Question 8. What is the neutralisation reaction?
Answer: When the effect of base is nullified by an acid and vice versa, it is called a neutralisation reaction.

Question 9. How does the chloride of lime differ chemically from calcium chloride?
Answer: The chloride of lime is CaOCl2, while calcium chloride is CaCl₂.

Question 10. What is meant by water of crystallisation in a substance? Explain with an example.
Answer: Water of crystallisation is the fixed number of water molecules present in one formula unit of a salt,

Example: CuSO₄.5H₂O

Question 11. How does the change occur in the pH values of milk when it changes to curd? Axis.
Answer: When milk changes to curd, it becomes acidic due to the formation of lactic acid, Thus its pH value decreases and becomes less than 6.

Question 12. Why does 1 M HCl solution have a higher concentration of H⁺ ions than 1 M CH₃COOH solution?
Answer: The HCl solution is a strong city and, therefore, ionises completely as compared to the CH₃ COOH solution which is a weak acid. Due to complete ionisation, it contains a high concentration of H⁺ ions.

Question 13. What are olfactory indicators? 
Answer:  The substances whose odour changes in acidic or basic media are called olfactory indicators.

Question 14. Which one of the following has the higher concentration of H+ ions? 1 M HCl or 1 M CH₃COOH?
Answer: 1 M HCl has a higher concentration of H⁺ ions, being a strong acid, it ionises completely to furnish H⁺ ions.

Question 15. What effect does an increase in the concentration of H⁺(aq) in a solution have on the pH of the solution?
Answer:

The pH of a solution decreases with the increase in the concentration of H⁺(aq). It is so because pH is the negative logarithmic value of H⁺(aq) a solution. More are the H⁺(aq) in a solution, more is the acidity, and less is the pH value of that solution.

Question 16. Why is HCl a stronger acid than acetic acid?
Answer: On dissociation, HCl yields larger (H⁺) hydrogen ions for the same concentration as compared to acetic acid. So it is stronger than acetic acid.

Question 17. Dry HCl gas does not change the colour of dry blue litmus. Give reasons.
Answer: H⁺ ions from HCl cannot ionise to give H⁺ ions in the absence of water. Acidic property like change in colour of litmus depends on the production of H⁺ ions, hence there is no colour change.

Question 18. How is the pH of a solution of an acid influenced when it is diluted?
Answer: On dilution, the concentration of hydrogen ions per unit volume decreases and hence pH of the solution increases. Since pH is the negative logarithmic value of the concentration of hydrogen ions.

Question 19. How will you test for the gas which is liberated when HCl acid reacts with an active metal?
Answer: When a burning candle is brought near the jar filled with hydrogen gas, it burns explosively with a pop sound.

Question 20. Which bases are called alkalies? Give an example of alkalies.
Answer:  Soluble bases are called alkalies,

Example: Sodium hydroxide (NaOH).

Question 21. Write a balanced chemical equation for the reaction between Sodium carbonate and hydrochloric acid indicating the physical state ofthe reactants and the products.
Answer:

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

Question 22. What is meant by pH and pH in pH?
Answer: p in pH stands for potenz and H is for hydrogen.

Question 23. Write the chemical name and chemical formula of washing soda.
Answer:

• Chemical name-Sodium carbonate
• Chemical formula-Na₂CO₃.10H₂O

Question 24. How is the concentration of hydronium ions (HO⁺) affected when a solution of an acid is diluted?
Answer:

When a given amount of acid is added to water, on diluting, the concentration of hydronium ions decreases because there are present a fixed amount of hydronium ions (H₃O⁺) per unit volume of the solution.

Question 25. How is the concentration of hydroxide ion (OH^–) affected when an excess base is dissolved in a solution of sodium hydroxide?
Answer: The concentration of hydroxide ions (OH^–) increases when the excess base (which also supplies OH^– ions) is dissolved in a solution of sodium hydroxide.

Question 26. You have two solutions, A and B. The pH of solution A is 6 and the pH of solution B is 8. Which solution has more hydrogen ion concentration? Which of these is acidic and which one is basic?
Answer: Lower pH means higher H⁺ ion concentration. Thus, solution ‘A’ has more H⁺ ion concentration. Therefore, solution A is acidic as the pH is less than 7 and solution B is basic as the pH is more than 7.

Question 27. What effect does the concentration of H⁺(aq) ions have on the nature of the solution?
Answer: More the H⁺(aq) ion concentration, the higher the acidic character of the solution

Question 28. Do the basic solution also have H⁺(aq) ions? If yes, then why are these basic?
Answer: Basic solutions have H⁺(aq) ions. But they are lesser in number than OH^– ions. Excess of OH^–(aq) ions counts for the basic character of basic solutions.

Question 29. Under what soil condition do you think a farmer would treat the soil of his field with quicklime(calcium oxide) slaked lime (calcium hydroxide) or chalk (calcium carbonate)?
Answer: Plants grow well in the pH range 6-8. So when soil becomes acidic, a farmer will do it. his fields with weak bases like quick lime or slaked lime.

Question 30. What is the common name of the compound CaOCl₂?
Answer: The common name of the compound, CaOCl₂ is bleaching powder.

Question 31. Why does an aqueous solution of an acid conduct electricity?
Answer: An aqueous solution of an acid contains charged particles which are responsible for the conduction of electricity.

Question 32. Why does dry HCl gas not change the colour of the dry litmus paper?
Answer: Dry HCl gas does not generate H⁺ ions and does not act as acid. Hence, cannot change the colour of dry litmus paper.

Question 33. Name the substance which on treatment with chlorine yields bleaching powder.
Answer: Slaked lime [Ca(OH)₂] or lime water on treatment with chlorine gives bleaching pow

Question 34. Name the sodium compound which is used for softening hard water.
Answer:  Sodium carbonate is used for softening hard water.

Question 35. Why does distilled water not conduct electricity, whereas rain water does ?
Answer:  Rainwater contains ions of acids, so it conducts electricity, whereas there are no ions in distilled water.

Question 36. Why do acids not show acidic behaviour in the absence of water?
Answer:  Acids in water give hydronium ions, which are responsible for their acidic behaviour. But in the absence of water acids do not generate hydronium ions and thus do not show acidic behaviour.

Question 37. Fresh milk has a pH of 6. How do you think the pH will change as it turns into curd? Explain your answer.
Answer: The pH of milk falls below 6 as it turns into curd due to the formation of lactic acid during this process.

Question 38. Plaster of Paris should be stored in a moisture-proof container. Explain why?
Answer: Plaster of Paris is calcium sulphate hemihydrate (CaSO₄.i H₂O). On exposure to moisture absorbs moisture and becomes gypsum (CaSO₄.i H₂O which does not have the required setting property.