molecular fraction

例句：

1. 1.The molecular fraction of the compound is important for its stability.
   化合物的分子分数对其稳定性很重要。
2. 2.The molecular fraction of water in a sample can be used to determine its purity.
   样品中水分子分数可以用来确定其纯度。
3. 3.The molecular fraction of the gas was determined using a gas chromatograph.
   使用气相色谱仪测定了气体的分子分数。