# How do you balance this chemical equation: N_2 + H_2 -> NH_3?

${N}_{2} + 3 {H}_{2} \to 2 N {H}_{3}$
Since there are $3$ hydrogen atoms in $N {H}_{3}$ and $2$ in ${H}_{2}$, we will need a multiple of $3 {H}_{2}$ on the left to balance the right hand side. Then notice that ${N}_{2} + 3 {H}_{2}$ does balance $2 N {H}_{3}$, so we're done.