When equal volume of $1 \mathrm{~M} \mathrm{~HCl}$ and $1 \mathrm{~M} \mathrm{~H}_2 \mathrm{SO}_4$ are separately neutralised by excess volume of $1 \mathrm{M}$ $\mathrm{NaOH}$ solution. $x$ and $y \mathrm{~kJ}$ of heat is liberated respectively. The value of $y / x$ is __________.