When hydrochloric acid is added to cobalt nitrate solution at room temperature, the following reaction takes place and the reaction mixture becomes blue. On cooling the mixture it becomes pink
\(\underset{\Large{pink}}{[Co(H_2O)_6]^{3+} (aq)} + 4Cl^-(aq) \rightleftharpoons \underset{\Large{blue}}{[CoCl_4]^{2-} (aq)} + 6H_2O(l)\)

On the basis of the information given above, mark the correct answer:

1.	∆ H > 0  for the reaction
2.	∆ H < 0  for the reaction
3.	∆ H = 0  for the reaction
4.	The sign of  ∆ H  cannot be predicted on the basis of the given information.

The pH of neutral water at $25°\mathrm{C}$ is 7.0. As the temperature increases, ionisation of water increases. However, the concentration of H⁺ ions and OH^- ions is equal. What will be the pH of pure water at 60°C ?

The ionisation constant of an acid, K_a , is the measure of the strength of an acid. The K_a values of acetic acid, hypochlorous acid and formic acid are $1.74\times {10}^{-5},<mspace\; width="1em"></mspace>3.0\times {10}^{-8}$ and $1.8\times {10}^{-4}$ , respectively. The  correct order of pH value of 0.1 mol dm^-3 solutions of these acids is:

1. Acetic acid > Hypochlorous acid > Formic acid

2. Hypochlorous acid < Acetic acid > Formic acid

3. Formic acid > Hypochlorous acid > Acetic acid

4. Formic acid < Acetic acid < Hypochlorous acid

${\mathrm{K}}_{{\mathrm{a}}_1},$ ${\mathrm{K}}_{{\mathrm{a}}_2}$ $\mathrm{and}$ ${\mathrm{K}}_{{\mathrm{a}}_3}$ are the respective ionisation constants for the following reactions.
\(\mathrm{H}_2 \mathrm{~S} \rightleftharpoons \mathrm{H}^{+}+\mathrm{HS}^{-}\)
\(\mathrm{HS}^{-} \rightleftharpoons \mathrm{H}^{+}+\mathrm{S}^{2-}\)
\(\mathrm{H}_2 \mathrm{~S} \rightleftharpoons 2 \mathrm{H}^{+}+\mathrm{S}^{2-}\)
The correct relationship between ${\mathrm{K}}_{{\mathrm{a}}_1},$ ${\mathrm{K}}_{{\mathrm{a}}_2}$ $\mathrm{and}$ ${\mathrm{K}}_{{\mathrm{a}}_3}$ is:
1. \(\mathrm{K}_{\mathrm{a}_3}=\mathrm{K}_{\mathrm{a}_1} \times \mathrm{K}_{\mathrm{a}_2} \)
2. \(\mathrm{K}_{\mathrm{a}_3}=\mathrm{K}_{\mathrm{a}_1}+\mathrm{K}_{\mathrm{a}_2} \)
3. \(K_{a_3}=K_{a_1}-K_{a_2} \)
4. \(\mathrm{K}_{\mathrm{a}_3}=\mathrm{K}_{\mathrm{a}_1} / \mathrm{K}_{\mathrm{a}_2}\)

Acidity of BF₃ can be explained on the basis of: 

1. Arrhenius concept

2. Bronsted Lowry concept 

3. Lewis concept

4. Bronsted Lowry as well as Lewis concept

The mixture that will produce a buffer solution when mixed in equal volumes is:

The value of the pH of \(0.01 \) \(\text{mol dm}^{-3}   \)\(\text{CH}_3\text{COOH}\) \(\left(K_a=1.74 \times 10^{-5}\right)\)  is:

Which of the following alternatives best describes the reaction A ⇌ B at its halfway point?
1. \(\Delta G^{\ominus}=0\)
2. \(\Delta G^{\ominus}>0\)
3. \(\Delta G^{\ominus}<0\)
4. \(\Delta G^{\ominus}=-RTlnK\)

On increasing the pressure, the direction in which the gas phase reaction proceeds to re-establish equilibrium is predicted by applying Le-Chatelier's principle. Consider the reaction,

${\mathrm{N}}_2\left(\mathrm{g}\right)+3{\mathrm{H}}_2\left(\mathrm{g}\right)\rightleftharpoons 2{\mathrm{NH}}_3\left(\mathrm{g}\right)$

Which of the following is correct, if the total pressure at which the equilibrium is established is increased without changing the temperature?