A solution of benzoic acid (a weak monobasic acid) is titrated with NaOH. The pH of the solution is 4.2 when half of the acid is neutralized. The dissociation constant of the acid will be:

1. $3.2\times {10}^{-5}$

2. $6.42\times {10}^{-4}$

3. $6.31\times {10}^{-5}$

4. $8.7\times {10}^{-8}$

The mixture that shows the maximum buffer capacity is:

1. $0.1 \mathrm{M} {\mathrm{CH}}_3\mathrm{COOH}+0.2 \mathrm{M}\hspace{0.17em}{\mathrm{CH}}_3\mathrm{COONa}$

2. $0.1 \mathrm{M} {\mathrm{CH}}_3\mathrm{COOH}+0.15 \mathrm{M}\hspace{0.17em}{\mathrm{CH}}_3\mathrm{COONa}$

3. $0.05 \mathrm{M} {\mathrm{CH}}_3\mathrm{COOH}+0.15 \mathrm{M}\hspace{0.17em}{\mathrm{CH}}_3\mathrm{COONa}$

4. $0.1 \mathrm{M} {\mathrm{CH}}_3\mathrm{COOH}+0.12 \mathrm{M}\hspace{0.17em}{\mathrm{CH}}_3\mathrm{COONa}$

The pH of a solution containing 0.1 mol of CH₃COOH, 0.2 mol of CH₃COONa, and 0.05 mol of NaOH in 1 L of solution is-

(pK_a of CH₃COOH=4.74 and log 5=0.7)

1. 4.56

2. 5.44

3. 5.04

4. 3.74

18 ml of mixture of acetic acid and sodium acetate required 6 ml of 0.1 M NaOH for neutralization of the acid and 12 ml of 0.1 M HCl for reaction with salt separately. If pK_a of the acid is 4.75, what is the pH of the mixture?

1. 5.05

2. 4.75

3. 4.5

4. 4.6

What is the minimum pH required to prevent the precipitation of ZnS in a solution that is 0.01 M ZnCl₂ and saturated with 0.10 M H₂S?

$[\mathrm{Given} : {\mathrm{K}}_{\mathrm{sp}} \mathrm{of} \mathrm{ZnS}={10}^{-21}, {\mathrm{K}}_{{\mathrm{a}}_1}\times {\mathrm{K}}_{{\mathrm{a}}_2} \mathrm{of} {\mathrm{H}}_2\mathrm{S}={10}^{-20}]$

1. 4

2. 3

3. 2

4. 1

Which of the following is an amphiprotic (can accept and give protons) ion?

1. ${\mathrm{HPO}}_3^{-}$

2. ${\mathrm{H}}_2{\mathrm{PO}}_2^{-}$

3. ${\mathrm{H}}_3{\mathrm{PO}}_4$

4. ${\mathrm{H}}_2{\mathrm{PO}}_4^{-}$

The ratio of F^- and HCOO^- in a mixture of 0.1 M HF $({\mathrm{K}}_{\mathrm{a}}=6.6\times {10}^{-4})$ and 0.2 M HCOOH $({\mathrm{K}}_{\mathrm{a}}=2\times {10}^{-4})is:$

A buffer solution is prepared by mixing 10 mL of 1.0 M acetic acid with 20 mL of 0.5 M sodium acetate which is then diluted
to 100 mL with distilled water. If the pK_a of ${\mathrm{CH}}_3\mathrm{COOH}$ is 4.76, the pH of the buffer solution prepared is -
1. 5.21

2. 4.76

3. 4.34

4. 5.35

What is the pH of a solution obtained by mixing equal volumes of two solutions, one with a pH of 3 and the other with a pH of 4?
[log 5.5=0.7404]

1. 3.26

2. 3.5

3. 4.0

4. 3.42

Solid AgNO₃ is added slowly to a buffer solution of pH=10 to precipitate AgOH. The [Ag⁺] concentration in the solution is $\left[{\mathrm{K}}_{\mathrm{sp}}\right(\mathrm{AgOH})={10}^{-10}]$

1. ${10}^{-4} \mathrm{M}$

2. ${10}^{-5} \mathrm{M}$

3. ${10}^{-6} \mathrm{M}$

4. ${10}^{-7} \mathrm{M}$