The pK_a of HCN is 9.30. The pH of a solution prepared by mixing 2.5 moles of KCN and 2.5 moles of HCN in water and making up the total volume to 500 ml will be:

1.	9.30	2.	8.30
3.	7.30	4.	10.30

What is the decreasing order of strength of the bases?

${\mathrm{OH}}^{-},<mspace\; width="1em"></mspace>{\mathrm{NH}}_2^{-},<mspace\; width="1em"></mspace>\mathrm{H}-\mathrm{C}\equiv {\mathrm{C}}^{-}<mspace\; width="1em"></mspace>\mathrm{and}<mspace\; width="1em"></mspace>{\mathrm{CH}}_3-{\mathrm{CH}}_2^{-}?$

1. ${\mathrm{CH}}_3-{\mathrm{CH}}_2^{-}>{\mathrm{NH}}_2^{-}>\mathrm{H}-\mathrm{C}\equiv {\mathrm{C}}^{-}>{\mathrm{OH}}^{-}$

2. $\mathrm{H}-\mathrm{C}\equiv {\mathrm{C}}^{-}>{\mathrm{CH}}_3-{\mathrm{CH}}_2^{-}>{\mathrm{NH}}_2^{-}>{\mathrm{OH}}^{-}$

3. ${\mathrm{OH}}^{-}>{\mathrm{NH}}_2^{-}>\mathrm{H}-\mathrm{C}\equiv {\mathrm{C}}^{-}>{\mathrm{CH}}_3-{\mathrm{CH}}_2^{-}$

4. ${\mathrm{NH}}_2^{-}>\mathrm{H}-\mathrm{C}\equiv {\mathrm{C}}^{-}>{\mathrm{OH}}^{-}>{\mathrm{CH}}_3-{\mathrm{CH}}_2^{-}$

The following equilibrium is established when hydrogen chloride is dissolved in acetic acid:

$$\(\small {\mathrm{HCl}+\mathrm{CH}_3 \mathrm{COOH} \rightleftharpoons \mathrm{Cl}^{-}+\mathrm{CH}_3 \mathrm{COOH}_2^{+}}\)

The set that characterizes the conjugate acid-base pair is:

Which of the following is an example of a reversible reaction?

A certain weak acid has a dissociation constant of $1.0\times {10}^{-4}.$ The equilibrium constant for its reaction with a strong base is

1. $1.0\times {10}^{10}$

2. $1.0\times {10}^{14}$

3. $1.0\times {10}^{-10}$

4. $1.0\times {10}^{-4}$

Find the condition under which CaF₂ (Ksp = 1.7 × 10⁻¹⁰) precipitate is formed
when equal volumes of two solutions are mixed.

1. \(10^{-2} \mathrm{M}\left[\mathrm{Ca}^{++}\right]+10^{-3} \mathrm{M}\left[\mathrm{~F}^{-}\right]\)
2. \(10^{-3} \mathrm{M}\left[\mathrm{Ca}^{++}\right]+10^{-5} \mathrm{M}\left[\mathrm{~F}^{-}\right]\)
3. \(10^{-4} \mathrm{M}\left[\mathrm{Ca}^{++}\right]+10^{-4} \mathrm{M}\left[\mathrm{~F}^{-}\right]\)
4. \(10^{-5} \mathrm{M}\left[\mathrm{Ca}^{++}\right]+10^{-3} \mathrm{M}\left[\mathrm{~F}^{-}\right]\)

Find the conditions that give the maximum yield of SO₃ for the exothermic reaction:

2SO₂(g) + O₂(g) ⇌ 2SO₃(g)

If a solution of 0.1 M NH₄OH and 0.1 M NH₄Cl has pH 9.25, then the pK_b of NH₄OH will be:

The compound with the highest pH among the following is:

1. CH₃COOK

2. Na₂CO₃ 

3. NH₄Cl

4. NaNO₃

The sharp pH change near the equivalence point in acid-base titration enables indicator detection. Which of the following equations correctly explains the pH change based on the concentration ratio of an indicator's conjugate acid (HIn) and base (In⁻) forms?