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Acids, Bases and Salts: MCQs and Answers with explanation

Acids, Bases and Salts: MCQs and Answers with explanation

1. Water cannot act as





... Answer is a)
Explanation: Lewis acid is a an electron pair acceptor. Water has an oxygen atom as a central atom. Oxygen has two bond pairs and two lone pairs of electrons. Due to presence of these elctrons pairs, oxgen cannot accept electron pair, so, water cannot act as lewis acid.

2. pH of 0.01M HCl solution is





... Answer is c)
Explanation: HCl is a strong acid and it is completely ionized in water. So, 0.01 M HCl soltution will produce, 0.01 M H+ ions and 0.01 M Cl- ions. Hence, pH = -log[H+] pH = -log(0.01) pH = 2

3. Aquous solution of ammonium chloride is





... Answer is b)
Explanation: Ammonium chloride (NH4Cl) is a salt of strong acid, HCl and a weak base, NH4OH. On dissolving in water, NH4Cl undergoes hydrolysis to produce strong acid (HCl) and weak base (NH4OH). As H+ ions produced by a strong acid are greater than OH- ions produced by weak base, so, solution becomes acidic.

4. An aqueous solution of which compound is basic?





... Answer is d)
Explanation: Potassium carbonate is a salt of a strong base (KOH) and a weak acid (H2CO3).So, solution of potassium carbonate is basic. Ammonium nitrate is a salt of a weak base (NH4OH) and a strong acid (HNO3).So, solution of ammonium nitrate is acidic. Calcium chloride is a salt of a strong base, (Ca(OH)2) and a strong acid (HCl).So, soltuion of calcium chloride is neutral. Ammonium acetate is a salt of a weak base (NH4OH) and a weak acid (CH3COOH).So, solution of ammonium acetate is a neutral.

5. Which statement about acids is not correct? An acid





... Answer is b)
Explanation: Presence of oxygen atom in an acid is not necessary condition. An acid may or may not contain oxygen atom. For example, HI, HBr, Hi etc without oxygen atoms.

6. If a liquid has a pH of 7.





... Answer is d)
Explanation: pH is related to concentration of hydrogen ions. If liquid has pH = 7, it means it has [H+] = [OH-]. So, liquid must be neutral.

7. When air is bubbled trhough pure water, the pH is lowered from 7.0 to 5.6, which gas in the air is responsible for this change.





... Answer is b)
Explanation: Carbon dioxide (CO2) is an acidic gas at it produces carbonic acid (H2CO3) when dissolves in water. So when air is bubbled throgh a pure water, pH is decresed due to presence of CO2 in air.

8. Which of the following oxides is classified incorrectly?





... Answer is d)
Explanation: Lead oxide (PbO) is amphoteric as it can react with both acid as well as with base.

9. If 25cm3 of 1 mole.dm-3 nitric acid is added to 50cm3 of 0.5 mole.dm-3 potassium hydroxide solution, what would be the pH of the resulting solution?





... Answer is b)
Explanation: Concentration of HNO3 = 1 mole.dm-3 Volume of HNO3 = 25cm3 = 0.025 dm3 No. of moles of HNO3 = Molarity × volume No. of moles of HNO3 = 1 x 0.025 No. of moles of HNO3 = 0.025 moles Concentration of KOH = 0.5 mole.dm-3 Volume of KOH = 50cm3 = 0.05 dm3 No. of moles of KOH = Molarity × volume. No. of moles of KOH = 0.5 × 0.05 No. of moles of KOH = 0.025 moles . Hence, HNO3 is a strong acid and KOH is a strong base. Both are of equal concentrations and produce equal number [H+]and [OH-]. Therefore, the resulting pH is neutral (7),

10. If dry citric acid crystals are placed on dry litmus paper they will





... Answer is d)
Explanation: An acid turns blue litmus paper red under aqeous conditions. However, under dry conditions, citric acid does not show acidic behaviour and dry litmus paper remains unchanged.

11. A base is a substane which will neutralize an acid. Which of these substances is not a base?





... Answer is c)
Explanation: Potassium chloride is a salt of a strong base (KOH) and a strong acid (HCl). Potassium chloride solution is a neutral and can not act as base.

12. A strong acid:





... Answer is b)
Explanation: A strong acid is alway completely ionized in solution form.

13. Which one of the following oxides dissolves in water to form acidic solution





... Answer is c)
Explanation: SO2 is oxide of non-metal and when it is dissolvedd in water, it produces an acidic solution. SO2 + H2O ----------> H2SO3

14. When crystals of copper sulphate are heated, then color changes from blue to white. This is caused by





... Answer is a)
Explanation: Crystals of copper sulphate (CuSO4.H2O) are blue in colour due to presence of water of crystallization in it. When crystals of copper sulphate are heated, then color changes from blue to white due to loss of water molecues.

15. The oxide of a metal was found to react with HCl along aqeous NaOH solution. Which of the following is the best description of the oxide?





... Answer is b)
Explanation: Amphoteric oxides have property of reacting with both acids and bases..
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