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

The pH of a solution obtained by mixing equal volume of solutions having pH=3 and pH=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. ${10}^{-7} \mathrm{M}$

If pK_b for ${\mathrm{CN}}^{-}$ at $25°\mathrm{C}$ is 4.7, the pH of 0.5 M aqueous NaCN solution is

1. 10

2. 11.5

3. 11

4. 12

A buffer solution is prepared by mixing 20 ml of 0.1 M CH₃COOH and 40 ml of 0.5 M CH₃COONa and then diluted by adding 100 ml of distilled water. The pH of the resulting buffer solution is (Given pKa CH₃COOH=4.76)

1. 5.76

2. 3.67

3. 2.48

4. 4.76

An acid-base indicator has ${\mathrm{K}}_{\mathrm{a}}=3.0\times {10}^{-5}$. The acid form of the indicator is red and the basic form is blue. The [H⁺] required to change the indicator from 75% red to 75% blue is

1. $8\times {10}^{-5} \mathrm{M}$

2. $9\times {10}^{-5} \mathrm{M}$

3. $1\times {10}^{-5} \mathrm{M}$

4. $3\times {10}^{-4} \mathrm{M}$