The mixture of salts $\mathrm{NaCl},\mathrm{NaBr},\mathrm{NaI}$ on adding cone. ${\mathrm{H}}_2{\mathrm{SO}}_4$ and followed by warming gives gases respectively :

When conc.${\mathrm{H}}_2{\mathrm{SO}}_4$  is added to a mixture of  $\mathrm{NaCl},\mathrm{NaBr},\mathrm{NaI}$ the resulting gases are, respectively,  $\mathrm{HCl},{\mathrm{Br}}_2$ and ${\mathrm{I}}_2$

Strong reducing agents HBr and HI are converted to  ${\mathrm{Br}}_2$ and ${\mathrm{I}}_2$ by ${\mathrm{H}}_2{\mathrm{SO}}_4$ respectively.

$$\begin{gathered} \mathrm{NaCl}+\text{ conc. }{\mathrm{H}}_2{\mathrm{SO}}_4\to {\mathrm{Na}}_2{\mathrm{SO}}_4+\mathrm{HCl} \\ \mathrm{NaBr}+\text{ conc. }{\mathrm{H}}_2{\mathrm{SO}}_4\to {\mathrm{Na}}_2{\mathrm{SO}}_4+{\mathrm{Br}}_2+{\mathrm{H}}_2\mathrm{O}+{\mathrm{SO}}_2 \\ \mathrm{NaI}+\text{ conc. }{\mathrm{H}}_2{\mathrm{SO}}_4\to {\mathrm{Na}}_2{\mathrm{SO}}_4+{\mathrm{I}}_2+{\mathrm{H}}_2\mathrm{O}+{\mathrm{H}}_2\mathrm{S} \end{gathered}$$