Question

One mole of $HCl\left(aq\right)$ is neutralised by one mole of $NaOH\left(aq\right)$. How many moles of $Ca(OH{)}_2$ are required to neutralise $10$ moles of $HCl\left(aq\right)$?

Answer 1

$Ca(OH{)}_2$ is diacidic base as it contains two $OH$ groups.
One mole of $Ca(OH{)}_2$ reacts with $2$ moles of $HCl$.
Hence, $10$ moles of $HCl$ will react with $\frac{10}{2}=5$ mol of $Ca(OH{)}_2$.