# MCQ | Ionic Equilibrium

Practice Test – I

Q:1. An acidic indicator HIn (Kin = 10–6) ionises as HIn H+ + In. The acid colour predominates over the basic colour when HIn is at least 10 times more concentrated than In ion. On the other hand basic colour predominates over the acid colour when the In ion is at least 5 times more concentrated than HIn. Hence pH range of the indicator is

(A) 5.0 – 6.7

(B) 7.0 – 8.7

(C) 5.3 – 7.0

(D) 7.0 – 8.1

Ans: (A)

Q:2.The correct statement amongst the following is

(A) A strong electrolyte remains completely dissociated at all dilutions

(B) Upon dilution the degree of dissociation of a weak electrolyte and number of ions per unit volume of its solution both increase.

(C) A strong electrolyte is completely ionised at all dilutions but not completely dissociated.

(D) pH of solution of a weak acid decreases with dilution.

Ans: (C)

Q:3. 4 M solution of a weak monobasic acid (x% ionized and pH = 3.0) is diluted to 1 M by adding water (distilled). Percentage ionisation and pH of solution after dilution will be respectively.

(A) 2x and 2.7

(B) 0.25x and 3.3

(C) 0.5x and 2.7

(D) 2x and 3.3

Ans: (D)

Q:4. pH of a buffer solution changes from 6.20 to 6.17 when 0.003 mole of acid is added to 500 mL of the buffer. The buffer capacity of the system is, therefore

(A) 0.1

(B) 0.3

(C) 0.2

(D) 0.4

Ans: (C)

Q:5. Ksp of CaSO4 is 2.4 × 10–5 at 25°C. In a solution containing Ca2+ions the precipitation of CaSO4 begins to occur when SO42– ion concentration in the solution is made just to exceed the value of 4.8 × 10–3M. Hence concentration of Ca2+ ion in the solution  is

(A) 200 ppm

(B) 40 ppm

(C) 400 ppm

(D) 100 ppm

Ans: (A)

Q:6. Correct statement regarding pure water amongst the following is

(A) It contains only single specie i.e. H2O molecules

(B) It contains three species: H2O (molecules), H+ and OH

(C) It contains only two species H3O+ and OH

(D) It contains three species H2O(molecules), H3O+ and OH

Ans: (D)

Q:7. There is a solution which is one molar w.r.t. each M2+and X3+ ions present in it. The Ksp of M(OH)2 and X(OH)3 are 4.0 ×10–10 and  2.7 ×10–14 respectively . If NH4OH solution is added gradually to the above solution which of the following will happen?

(A) Both M(OH)2 and X(OH)3 will precipitate together

(B) M(OH)2 will precipitate first.

(C) X(OH)3 will precipitate first

(D) None of these will precipitate with NH4OH solution

Ans: (B)

Q:8. 20 mL of a weak acid HX is titrated against 0.1 M NaOH. At the point of half equivalence the pH of solution is 5.7. Hence Ka of acid is

(A) 7.0 × 10–5

(B) 2.0 × 10–5

(C) 7.0 × 10–4

(D) 2.0 × 10–6

Ans: (D)

Q:9. If an aqueous solution at 25°C has twice as many OH as pure water its pOH will be

(A) 6.699

(B) 7.307

(C) 7

(D) 6.98

Ans: (A)

Q:10. Solubility of AgCl in water, 0.01 M CaCl2, 0.01 M NaCl and 0.05 M AgNO3 are S1, S2, S3 and S4 respectively then.

(A) S1 > S2 > S3 > S4

(B) S1 > S3 > S2 > S4

(C) S1 > S2 = S3 > S4

(D) S1 > S3 > S4 < S2

Ans: (B)

Q:11. pH of Ba(OH)2 solution is 12. Its solubility product is

(A) 10–6M3

(B) 4 × 10–6M3

(C) 0.5 × 10–7M3

(D) 5 × 10–7M3

Ans: (D
)

Q:12. The hydrolysis constant for ZnCl2 will be

(A) $K_h = \frac{K_w}{K_b}$

(B) $K_h = \frac{K_w^2}{K_b}$

(C) $K_h = \frac{K_w^2}{K_b^2}$

(D) $K_h = \frac{K_b}{K_w^2}$

Where Kb is effective dissociation constant of base Zn++

Ans: (B)

Q:13. If the degree of ionization of water be 1.8 × 10-9 at 298 K. Its ionization constant will be

(A) 1.8 × 10-16

(B) 1 × 10-14

(C) 1 × 10-16

(D) 1.67 × 10-14

Ans: (D)

Q:14. When a solution of benzoic acid was titrated with NaOH the pH of the solution when half the acid neutralized was 4.2. Dissociation constant of the acid is

(A) 6.31 × 10-5

(B) 3.2 × 10–5

(C) 8.7 × 10–8

(D) 6.42 × 10–4

Ans: (A)

Q:15. 10-2 mole of NaOH was added to 10 litre of water. The  pH  will change by

(A) 4

(B) 3

(C) 11

(D) 7

Ans: (A)

Q:16. 0.1 M solution of which of the following substances is most acidic

(A) NH4Cl

(B) KCN

(C) AlCl3

(D) NaC2H3O2

Ans: (A)

Q:17. The following reaction takes place in the body
CO2 + H2O $\rightleftharpoons$ H2CO3 $\rightleftharpoons$ H+ + HCO3.   If CO2 escapes from the system

(A) pH decreases

(B) [H+] will decrease

(C) [H2CO3] remains the same

(D)forward reaction will be promoted

Ans: (B)

Q:18.The solubility of A2X5 is x mole dm-3. Its solubility product is

(A) 36 x6

(B) 64 x 104x7

(C) 126 x 7

(D)1.25 x 104x7

Ans: (D)

Q:19. The solubility of CH3CO2Ag would be least amongst the following
solvents in

(A) acidic solution of pH = 3

(B) basic solution of pH = 8

(C) neutral  solution of pH = 7

(D) pure water

Ans: (B)

Q:20. If Kh (hydrolysis constant) for anilinium ion is 2.4 x 10-5M, then Kb for
aniline will be

(A) 4.1 x 1010

(B) 4.1 x 10‑10

(C) 2.4 x 109

(D) 2.4 x 10-19

Ans: (B)

Q:21. Acetic acid dissolved in ammonia will be

(A) Highly conducting

(B) Less conducting

(C) Can’t say

(D) More conducting than that in water

Ans: (D)

Q:22. The equilibrium constant of the reaction:

A + H2O $\rightleftharpoons$ HA + OH

is 108 times more than ionic product of water at 25°C. Hence Ka of weak acid will be

(A) 10–8

(B) 10–6

(C) 10–14

(D) None of these

Ans: (A)

Q:23. If we plot α2 verses volume V we will get

(A) a straight line with slope value equal to Kdissociation  ­

(B) a  straight line with slope equal to Keq

(C) an exponential curve

(D) a parabola

Ans: (A)

Q:24. Equal volumes of two solutions of a strong acid having pH 3 and pH 4 are mixed together. The pH of the resulting solution will then be equal to

(A) 3.5

(B) 3.26

(C) 7

(D) 1.0

Ans: (B)

Q:25. When equal volumes of following solution are mixed, precipitation of AgCl
(Ksp = 1.8 x 10-10) will occur only with

(A) 10-4M; Ag+ and 10-4M; Cl

(B)10-5M; Ag+ and 10-5M; Cl

(C) 10-6M; Ag+ and 10-6M; Cl

(D)10-10M; Ag+ and 10-10M; Cl

Ans: (A)

Q:26. Let Kw at 100°C be 5.5 × 10-13 M2. If an aqueous solution at this temperature has
pH = 6.2. Its nature will be

(A) acidic

(B) alkaline

(C) neutral

(D) can’t say

Ans: (B)

Q: ­27. Dissociation constant of two acids HA & HB are respectively 4 × 10-10 & 1.8 × 10-5 whose pH value will be higher for a given molarity:

(A) HA

(B) HB

(C) Both same

(D) Can’t say

Ans: (A)

Q:28. pH value of pure water at 0°C will be

(A) Greater than 7

(C) Less than 7

(C) 7

(D) All the three

Ans: (A)

Q:29. The pH of a buffer is 6.745. When 0.01 mole of NaOH is added to 1 litre of it, the pH changes to 6.832. Its buffer capacity is

(A) 0.187

(B) 0.0115

(C) 0.076

(D) 0.896

Ans: (B)

Q:30. The aqueous solution of potash alum is acidic due to hydrolysis of

(A) K+

(B) Al3+

(C) SO4– –

(D) presence of acid in its crystal as impurity