乙烯、乙醛、乙酸、葡萄糖的混合物中，碳元素的质量分数为66%，则氧元素的质量分数为
A．33%
B．27%
C．30%
D．23%
答案：D
题目分析：乙烯分子式为C2H4，乙醛的分子式是C2H4O，乙酸的分子式为C2H4O2，葡萄糖分子式为C6H12O6，各物质分子中N（C）:N（H）＝1:2，则碳元素与氢元素的质量之比为12:2＝6:1，故混合物中碳元素与氢元素的质量之比为6:1。碳元素的质量分数为66%，则氢元素的质量分数＝66%÷6＝11%，所以氧元素的质量分数为1－66%－11%＝23%，答案选D。
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