2008年北京奥运会主体育场的外形好似“鸟巢 (The Bird Nest).有一类物质也好似鸟巢.如化学式是B5H9的五硼烷．下列有关五硼烷的说法错误的是( )A．五硼烷属于化合物B．五硼烷的相对分子质量是64C．五硼烷中硼元素和氢元素的质量比为5:9D．1个五硼烷分子由5个硼原子和9个氢原子构成题目和参考答案——青夏教育精英家教网—

题目内容

2008年北京奥运会主体育场的外形好似“鸟巢”（The Bird Nest），有一类物质也好似鸟巢，如化学式是B₅H₉的五硼烷（见图）．下列有关五硼烷的说法错误的是（）

A．五硼烷属于化合物
B．五硼烷的相对分子质量是64
C．五硼烷中硼元素和氢元素的质量比为5：9
D．1个五硼烷分子由5个硼原子和9个氢原子构成

【答案】分析：根据五硼烷的化学式和结构来回答，依据其元素组成来判断物质的种类，计算相对分子质量和各元素的质量比时，一定不要忽略各元素的原子个数．
解答：解：A、五硼烷属于化合物，因为里面含有两种元素．
B、五硼烷的相对分子质量=11×5+1×9=64．
C、五硼烷中硼元素和氢元素的质量比11×5：1×9=55：9．
D、五硼烷分子由5个硼原子和9个氢原子构成．
故选C
点评：化学式中元素的质量比和原子个数比一定要分清，不要因为粗心而失分．

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