MnO₂ and H₂SO₄ added to NaCI , the greenish yellow gas liberated is

Yellowish-green gas (chlorine) with suffocating odour is evolved when the sodium chloride mixed with manganese dioxide is heated with concentrated ${\mathrm{H}}_2{\mathrm{SO}}_4$
$\begin{array}{l}\mathrm{NaCl}+{\mathrm{H}}_2{\mathrm{SO}}_4\to {\mathrm{NaHSO}}_4+\mathrm{HCl}\\ {\mathrm{MnO}}_2+4\mathrm{HCl}\to {\mathrm{MnCl}}_2+2{\mathrm{H}}_2\mathrm{O}+{\mathrm{Cl}}_2\end{array}$