问题 选择题

有铁的氧化物样品,用140ml0.5mol/L的盐酸恰好使其完全溶解,所得溶液还能吸收标准状况下氯气56ml,使其中的Fe2+全部转化为Fe3+,该样品可能的化学式是(  )

A.Fe2O3

B.Fe3O4

C.Fe5O7

D.Fe4O5

答案

答案:C

题目分析:n(HCl)="0.14L×0.5mol/L=0.07" mol,n(Cl2)="0.0025" mol,由于发生反应:2Fe2++Cl2=2Fe3++2Cl,(

n(Fe2+)=0.5n(Cl2)="0.005" mol,最后溶液为FeCl3溶液,根据原子守恒可知;3n(Fe2++Fe3+)= n(Fe3+)最后=n(Cl-总)= n(HCl)+2n(Cl2)=" 0.07" mol+0.005 mol ="0.075" mol,所以n(Fe2++Fe3+)="0.025" mol,n(Fe3+)="0.02" mol,n(Fe2+)、n(Fe3+)的比为1:4。然后将选项中的各个复杂的氧化物变形为aFeO .bFe2O3形式。A无Fe2+离子,错误。B化学式变形为FeO .Fe2O3的化合物,二者的物质的量的比为1:2,错误。C.化学式变形为FeO. 2Fe2O3的化合物,二者的物质的量的比为1:4,正确。D 为2 FeO .Fe2O3的化合物,二者的物质的量的比为1:1,错误。

阅读理解

阅读理解:

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carefully the question, try to understand the exact meaning of each. When you have at last finish your exam,

read over your answers, correct the mistakes if there are any and be sure that you have not missed anything out.

1. How can we do well in an exam? [ ]

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A. not useful

B. helpful

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D. hard to understand

问答题