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    精英家教网 > 初中英语 > 题目详情
    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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