What are the coefficients that would balance the chemical equation below? Mg + H3PO4 -> Mg3(PO4)2 + H2
O 3, 2, 1,3
O 3, 2, 2, 3
O 1, 1, 1, 1
O 6, 4, 2, 6

The coefficients :  3, 2, 1,3

Given

Reaction

Mg + H3PO4 -> Mg3(PO4)2 + H2

Required

The coefficients

Solution

Steps to balance reactions:

1. Give a coefficient(The most complex compound is assigned a coefficient of 1)

aMg + bH₃PO₄ ⇒ Mg₃(PO₄)₂ + cH₂

2. Make an equation

Mg, left = a, right = 3 ⇒a=3

P, left = b, right = 2⇒b=2

H, left = 3b, right = 2c⇒3b=2c⇒3.2=2c⇒2c=6⇒c=3

The equation becomes :

3Mg + 2H₃PO₄ ⇒ Mg₃(PO₄)₂ + 3H₂