Balance the chemical equation NH3 + H2SO4 → (NH4)2SO4

What you are balancing in this reaction

You need the same number of each type of atom on both sides of the arrow. Here, the product is ammonium sulfate, $(NH_4)_2SO_4$, which contains two ammonium groups.

Count atoms in the unbalanced equation

Unbalanced: $$NH_3 + H_2SO_4 \rightarrow (NH_4)_2SO_4$$

Atom counts:

• Left: $N=1$ (from $NH_3$), $H=3+2=5$, $S=1$, $O=4$
• Right: $(NH_4)_2SO_4$ has $N=2$, $H=8$, $S=1$, $O=4$

Nitrogen and hydrogen do not match.

Fix the coefficient on ammonia

Because the product has $N=2$, put a 2 in front of $NH_3$: $$2NH_3 + H_2SO_4 \rightarrow (NH_4)_2SO_4$$

Now recount:

• Left: $N=2$, $H=2\cdot 3 + 2 = 8$, $S=1$, $O=4$
• Right: $N=2$, $H=8$, $S=1$, $O=4$

Everything matches, so it is balanced.

Quick check

Sulfur and oxygen were already balanced because $SO_4$ appears unchanged on both sides; the main job was matching the two $NH_4$ groups by using $2NH_3$.