# When the following equation is balanced, what is the coefficient for Mg? Mg(s) + HCl(aq) -> MgCl_2(aq) + H_2(g)

May 22, 2017

1 is the coefficient. See below.

#### Explanation:

So, to balance a chemical equation we make the number of each element the same on both sides.

We have:
Mg (s) + HCl (aq) → MgCl_2 (aq) + H_2 (g)

LHS
Mg= 1
H= 1
Cl= 1

RHS
Mg= 1
Cl=2
H=2

To make Cl and H have 2 on both sides, we place a 2 in front of the HCl

Mg (s) + 2HCl (aq) → MgCl_2 (aq) + H_2 (g)

LHS
Mg=1, H=2, Cl=2

RHS
Mg=1, H=1, Cl=2

Thus the equation is balanced and the coefficient of Mg is 1, which is understood so it is not written in the final equation.