please help me with this chemistry problem.

1) Write out a balanced chemical reaction equation for the reaction of magnesium with hydrochloric acid,

and then

What is the Theoretical Yield after balancing the chemical equation?

2 answers

Metal + acid ---> metal salt + hydrogen gas
Mg + HCl --> MgCl2 + H2

If you place the correct coefficient in front of HCl, you will have the chemical equation balanced for Cl and H (which it is not now).
The balanced chemical equation assumes a theoretical yield of 100%. To calculate the actual yield we must know the amounts of reactants (Mg and HCl) actually used.