[题目]下列关于空气成分的叙述正确的是( ).A．空气中氮气和氧气的体积比约为4∶1B．空气的成分按质量计算.氮气占78%.氧气占21%C．从液态空气中能分离出氮气.不能分离出氧气和稀有气体D．空气中含量最多且性质又不活泼的是稀有气体题目和参考答案——青夏教育精英家教网—

题目内容

【题目】下列关于空气成分的叙述正确的是( )。

A．空气中氮气和氧气的体积比约为4∶1

B．空气的成分按质量计算，氮气占78%，氧气占21%

C．从液态空气中能分离出氮气，不能分离出氧气和稀有气体

D．空气中含量最多且性质又不活泼的是稀有气体

【答案】A

【解析】

试题分析：A．空气中氮气和氧气的体积比约为4∶1。此项正确。B．空气的成分按体积分数计算，氮气占78%，氧气占21%；C．从液态空气中能分离出氮气、氧气和稀有气体。D．空气中含量最多且性质又不活泼的是氮气。

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