Question

Write a balanced chemical equation for the reaction of magnesium with hydrochloric acid (HCI (aq) to form Magnesium chloride and hydrogen gas:

Answer 1

The equation is
Mg + 2HCl -> MgCl2 +H2

Answer 2

Mg (s) + HCl (aq) → MgCl₂(s) + H₂(g)

Looking at the equation :

We have 1 Mg at the left hand side and 1 Mg as well on the right hand side.
So that is balanced.

We have 1 H at the left hand side and 2 H on the right hand side.
So that is not balanced. Same for Chlorine. Cl.

We add 2 to the HCl on the left hand side and that balances it.

Mg(s) + 2HCl(aq) → MgCl₂(s) + H₂(g)