What is the concentration of $$\mathrm{OH}^{-}$$ ion in a solution containing $$0.05 \mathrm{~M} \mathrm{~H}^{+}$$ ions?

Calculate the $$\mathrm{pH}$$ of $$1.36 \times 10^{-2} \mathrm{M}$$ solution of perchloric acid.

Find solubility in terms of $$\mathrm{mol} \mathrm{~L}^{-1}$$ if solubility product of silver bromide is $$6.4 \times 10^{-13}$$.

Calculate the concentration of $$\mathrm{H}^{+}$$ ions in a solution if pOH is 11.