# How do you balance P_4 + O_2 -> 2P_2O_3?

Jun 6, 2016

Count the number of atoms on each side to make sure they have the same number of atoms.

On the left side (or left of arrow),
P = 1 $\times$ 4 = 4 atoms of P
O = 1 $\times$ 2 = 2 atoms of O

On the right side
P = 2 $\times$ 2 = 4 atoms of P
O = 2 $\times$ 3 = 6 atoms of O

P is balanced but O isn't.

Find the lowest common multiple (LCM) of number of atoms present in O.
The LCM between 2 and 6 is 6.
On the left hand side, we need to make the number of atoms of O from 2 to become 6 by multiplying 3.
So insert a 3 in front of ${O}_{2}$ therefore its composed of 6 atoms.

Check your equation now:
${P}_{4} + 3 {O}_{2} \implies 2 {P}_{2} {O}_{3}$

Now double check to make sure the number of atoms are same on both side. - IMPORTANT

P = 4 atoms on left side and 4 atoms on right side - BALANCED
O = 6 atoms on left side and 6 atoms on right side - BALANCED

If they're all balanced, you're good to go write your balanced equation.

Overall, your balanced equation should look like:
${P}_{4} + 3 {O}_{2} \implies 2 {P}_{2} {O}_{3}$