When $\mathrm{KBr}$ is treated with conc. ${\mathrm{H}}_2{\mathrm{SO}}_4$ reddish-brown gas has evolved. The gas liberated is

 When  $\mathrm{KBr}$ is treated with conc. ${\mathrm{H}}_2{\mathrm{SO}}_4$ then brown gas is evolved which is ${\mathrm{Br}}_2$ gas. The reaction can be written as,

$\mathrm{KBr}+{\mathrm{MnO}}_2+3{\mathrm{H}}_2{\mathrm{SO}}_4\to {\mathrm{MnSO}}_4+2{\mathrm{KHSO}}_4+{\mathrm{Br}}_2\left(g\right)$