4NH3 + 502 --> 4NO + 6H20 How much excess reactant is leftover after if 6.30g of ammonia react with
1.80g of oxygen?

5.52 g

Explanation:

First we convert the given masses of both reactants into moles, using their respective molar masses:

Now we calculate with how many NH₃ moles would 0.056 O₂ moles react, using the stoichiometric coefficients:

As there more NH₃ moles than required, NH₃ is the excess reactant.

Then we calculate how many NH₃ moles remained without reacting:

Finally we convert NH₃ moles into grams: