This is a balanced chemical equation for the reaction between manganese dioxide $MnO2$ and hydrochloric acid $HCl$ producing manganese chloride $MnCl2$, chlorine gas $Cl2$, and water $H2O$:

4 MnO2 + 16 HCl = 4 MnCl2 + 8 Cl2 + 2 H2O