Question

Identify the gas evolved when concentrated hydrochloric acid is made to react with manganese dioxide

Answer 1

hey bro,

HCl - acid
MgO - Base(generally metal oxides are always base)

and
Base (aq) + Acid( aq) ------ Salt(aq) + H2 (g)

so we finally get Hydrogen gas as a result

Answer 2

hydrogen gas is evolved when come. HCL reacts with manganese dioxide