# How do you balance P_4 + Br_2 -> PBr_3?

Mar 7, 2016

We must make sure the number of molecules in each element on each side of the equation are equal.

#### Explanation:

The lowest number of ${P}_{4}$ that we can have is $1 {P}_{4}$, which means one molecule of 4 atoms of phosphorus.

This means we need 4 P atoms on the other side. We do this by making the equation:

$1 {P}_{4} + B {r}_{2} \to 4 P B {r}_{3}$

This means that we have (4 xx 3 = 12) atoms of bromine. To finish the balancing process, we need to balance the bromine on the other side of the equation. It would be $6 b {r}_{2}$ to make 12 atoms of bromine.

So, your equation will be ${P}_{4} + 6 B {r}_{2} \to 4 P B {r}_{3}$

Hopefully this helps!