Chlorine can be prepared in the laboratory by the reaction of
manganese dioxide with hydrochloric acid, HCl(aq), as described by
the chemical equation MnO2 (s) + 4HCl (aq) => MnCl2 + H2o + Cl2
How much MnO2(s) should be added to excess HCl(aq) to obtain 125 mL
of Cl2(g) at 25 °C and 805 Torr?