Corban E. answered 11/15/20
AP Chemistry Tutor and Former Teacher (Gen Chem, IB, O-Level, A-Level)
metal+acid→ionic compound+hydrogen gas
it's a single replacement reaction
Ba=+2 ion
Cl=-1 ion
H is diatomic as an atom
HCl(aq) because it's a solution.
BaCl2(aq) because it's the solution after the reaction.
Ba(s)+2HCl(aq)→H2(g)+BaCl2(aq)