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. ${10}^{-7} \mathrm{M}$

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. $3\times {10}^{-4} \mathrm{M}$

The self-ionization constant for pure formic acid, K = [\(H C O O H_{2}^{+} \left]\right. \left[\right. H C O O^{-} \left]\right.\) ] has been estimated as \(\left(10\right)^{- 4}\) at room temperature. The percentage of formic acid molecules in pure formic acid that are converted to formate ions is

\(\left(\right. Given : d_{HCOOH} = 1 . 22\ g / cc \left.\right)\)

1. 0.0185%

2. 0.0073%

3. 0.074%

4. 0.037%

AgOH is added to NaCl solution to form AgCl precipitate. After the precipitation, the pH of the solution is 8. The [Cl^-] is $({\mathrm{K}}_{\mathrm{sp}} \mathrm{of} \mathrm{AgCl}={10}^{-12}, {\mathrm{K}}_{\mathrm{sp}} \mathrm{of} \mathrm{AgOH}={10}^{-10})$

1. ${10}^{-6} \mathrm{M}$

2. ${10}^{-4} \mathrm{M}$

3. ${10}^{-8} \mathrm{M}$

4. ${10}^{-10} \mathrm{M}$