What is the value of pOH if a buffer solution is prepared by mixing equal volumes of $0.4 \mathrm{~M} \mathrm{~NH}_4 \mathrm{OH}$ and $0.5 \mathrm{~M} \mathrm{~NH}_4 \mathrm{Cl}$ solutions. $\left(\mathrm{pK}_{\mathrm{b}}=4.730\right)$

Which of the following salt solutions turns red litmus blue?

The solubility product of $$\mathrm{PbCl}_2$$ at $$298 \mathrm{~K}$$ is $$3.2 \times 10^{-5}$$. What is its solubility in $$\mathrm{mol} \mathrm{dm}{ }^{-3}$$ ?

Identify base$$_2$$ for following equation according to Bronsted-Lowry theory.

$$\mathrm{HCl}_{(\mathrm{aq})}+\mathrm{H}_2 \mathrm{O}_{(l)} \rightleftharpoons \mathrm{H}_3 \mathrm{O}_{(\mathrm{aq})}^{+}+\mathrm{Cl}_{(\mathrm{aq})}^{-}$$