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

The ionisation constant of an acid, $K_a$ is the measure of strength of an acid. The $K_a$ values of acetic acid, hypochlorous acid and formic acid are $1.74 \times 10^{-5}, 3.0 \times 10^{-8}$ and $1.8 \times 10^{-4}$ respectively. Which of the following orders of pH of $0.1 \mathrm{~mol} \mathrm{dm}^{-3}$ solutions of these acids is correct?

$K_{a_1}, K_{a_2}$ and $K_{a_3}$ are the respective ionisation constants for the following reactions.

$$\begin{aligned} & \mathrm{H}_2 \mathrm{~S} \rightleftharpoons \mathrm{H}^{+}+\mathrm{HS}^{-} \\ & \mathrm{HS}^{-} \rightleftharpoons \mathrm{H}^{+}+\mathrm{S}^{2-} \\ & \mathrm{H}_2 \mathrm{~S} \rightleftharpoons 2 \mathrm{H}^{+}+\mathrm{S}^{2-} \end{aligned}$$

The correct relationship between $K_{a_1}, K_{a_2}, K_{a_3}$ is

Acidity of $\mathrm{BF}_3$ can be explained on the basis of which of the following concepts?

Which of the following will produce a buffer solution when mixed i equal volumes?