实验室用锌粒与稀硫酸反应制取氢气，欲收集到较纯净的氢气，最佳收集方法是？
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Correct answer
C. 排水法
Principle or equation
氢气密度小于空气且难溶于水，排水法收集的气体纯度更高。
Why this answer is correct
排水法可避免空气混入，收集的氢气较纯净；排空气法可能混有空气。
Example
用排水集气法收集氢气时，导管口有气泡连续均匀冒出后开始收集。
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