例 1　在测定空气成分的实验中 ,若所用红磷量偏少 ,则测得的氧气的体积分数将偏.分析　教材中测定空气中氧气体积分数实验的原理是 :足量的红磷与空气中的氧气反应生成固态的五氧化二磷 ,导致玻璃钟罩内气体压强减小 ,水槽中的水在外界大气压的作用下进入钟罩内 ,且进入钟罩内 Example 1 In the experiment of determining the air composition, if the amount of red phosphorus used is too small, the measured volume fraction of oxygen will be biased. The principle of determining the volume fraction of oxygen in air is as follows: sufficient amount of red phosphorus and air The oxygen in the reaction produces a solid phosphorus pentoxide, which results in a decrease in the gas pressure in the glass bell jar. The water in the water tank enters the bell jar under the external atmospheric pressure and enters the bell jar.