Explanation:
[tex]31.5 \: g \: aommnia \: \times \: \frac{1 \: mol \: ammonia}{8 \: g \: ammonia \: } \: \times \frac{3 \: mol \: hydrogen}{2 \: mol \: ammonia} \: \times \frac{1 \: g \: hydrogen}{1 \: mol \: hydrogen} = \: 5.90625 \: g \: hydrogen \: must \: react \: [/tex]