CBSE - Chemistry - Acids, Bases and Salts

15. The pH of the gastric juices released during digestion is
(a) less than 7
(b) more than 7
(c) equal to 7
(d) equal to 0
Ans. (a) less than 7
Explanation: Refer to explanation for previous question


16. Which of the following phenomena occur, when a small amount of acid is added to water?
(i) Ionisation
(ii) Neutralisation
(iii) Dilution
(iv) Salt formation
(a) (i) and (ii)
(b) (i) and (iii)
(c) (ii) and (iii)
(d) (ii) and (iv)

Ans. (b) (i) and (iii)
Explanation: No base is being added, so (ii) and (iii) cannot happen. When acid is dissolved in water, it breaks into its ions.

17. Which one of the following can be used as an acid�base indicator by a visually impaired student?
(a) Litmus
(b) Turmeric
(c) Vanilla essence
(d) Petunia leaves
Ans. (c) Vanilla essence
Explanation: Vanilla works as olfactory indicator, hence it can be used by visually impaired student.

18. Which of the following substance will not give carbon dioxide on treatment with dilute acid?
(a) Marble
(b) Limestone
(c) Baking soda
(d) Lime
Ans. (d) Lime
Explanation: Other options show carbonate or hydrogen carbonate. Hence, they will give carbon dioxide on reaction with acid. But lime contains hydroxide and hence will not give carbon dioxide on reaction with acid

19. Which of the following is acidic in nature?
(a) Lime juice
(b) Human blood
(c) Lime water
(d) Antacid
Ans. (a) Lime juice
Explanation: Other are alkaline.

20. In an attempt to demonstrate electrical conductivity through an electrolyte, the following apparatus (Figure 2.1) was set up. Which among the following statement(s) is(are) correct?
(i) Bulb will not glow because electrolyte is not acidic
(ii) Bulb will glow because NaOH is a strong base and furnishes ions for conduction.
(iii) Bulb will not glow because circuit is incomplete
(iv) Bulb will not glow because it depends upon the type of electrolytic solution
(a) (i) and (iii)
(b) (ii) and (iv)
(c) (ii) only
(d) (iv) only

Ans. (c) (ii) only


21. Which of the following is used for dissolution of gold?
(a) Hydrochloric acid
(b) Sulphuric acid
(c) Nitric acid
(d) Aqua regia
Ans. (d) Aqua regia
Explanation: Gold is a noble metal and does not react with even concentrated acids.
Aqua regia is made by mixing nitric acid and hydrochloric acid in 1:3 ratio. It can dissolve even gold and platinum.

22. Which of the following is not a mineral acid?
(a) Hydrochloric acid
(b) Citric acid
(c) Sulphuric acid
(d) Nitric acid
Ans. (b) Citric acid
Explanation: It is an organic acid.

23. Which among the following is not a base?
(a) NaOH
(b) KOH
(c) NH₄OH
(d) C₂H₅OH
Ans. (d)C₂H₅OH
Explanation: It is alcohol

24. Which of the following statements is not correct?
(a) All metal carbonates react with acid to give a salt, water and carbon dioxide
(b) All metal oxides react with water to give salt and acid
(c) Some metals react with acids to give salt and hydrogen
(d) Some non-metal oxides react with water to form an acid
Ans. (b) All metal oxides react with water to give salt and acid
Explanation: Metal oxides are basic in nature. They give alkaline solution when dissolved in water.

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


(a) A�(ii), B�(i), C�(iv), D�(iii)
(b) A�(iii), B�(ii), C�(iv), D�(i)
(c) A�(iii), B�(iv), C�(i), D�(ii)
(d) A�(ii), B�(iv), C�(i), D�(iii)
Ans. (c) A-(iii), B-(iv), C-(i), D-(ii)
Explanation: Bleaching powder has got its name because of bleaching (decolourizing) property. Baking soda is used as antacid (as common household remedy). Sodium chloride (common salt) is used for making various chemicals through chloralkali process.



26. Equal volumes of hydrochloric acid and sodium hydroxide solutions of same concentration are mixed and the pH of the resulting solution is checked with a pH paper. What would be the colour obtained? (You may use colour guide given in Figure 2.2)

(a) Red
(b) Yellow
(c) Yellowish green
(d) Blue
Ans. (c) Yellowish green
Explanation: Neutralisation reaction takes place when hydrochloric acid and sodium hydroxide are mixed


27. Which of the following is(are) true when HCl (g) is passed through water?
(i) It does not ionise in the solution as it is a covalent compound.
(ii) It ionises in the solution.
(iii) It gives both hydrogen and hydroxyl ion in the solution.
(iv) It forms hydronium ion in the solution due to the combination of hydrogen ion with water molecule
(a) (i) only
(b) (iii) only
(c) (ii) and (iv)
(d) (iii) and (iv)
Ans. (c) (ii) and (iv)
Explanation: Any acid produces hydrogen ion (H+) which is present as hydronium ion(H₃O⁺) because of combination with water molecule.

28. Which of the following statements is true for acids?
(a) Bitter and change red litmus to blue
(b) Sour and change red litmus to blue
(c) Sour and change blue litmus to red
(d) Bitter and change blue litmus to red
Ans. (c) Sour and change blue litmus to red

29. Which of the following are present in a dilute aqueous solution of hydrochloric acid?
(a) H₃O⁺ + Cl⁻
(b) H₃O⁺ + OH⁻
(c) Cl⁻  + OH⁻
(d) unionised HCl
Ans. (a) H₃O⁺ + Cl

Explanation: Any acid produces hydrogen ion (H+) which is present as hydronium ion(H₃O⁺) because of combination with water molecule.