这个化学反应需要化学计量比的氢气和氧气才能完全进行。

The chemical reaction requires ___stoichiometric amounts of hydrogen and oxygen to proceed completely.

这种化学计量比的氮气和氢气混合物是合成氨的最佳原料。

This ___stoichiometric mixture of nitrogen and hydrogen is the optimal raw material for ammonia synthesis.