问题 选择题

若NA表示阿伏加德罗常数的数值,下列说法正确的是

A.1 mol氦气分子中含2NA个氦原子

B.在0℃、101kPa时,22.4L氢气中含有NA个氢原子

C.在标准状况下,22.4L空气中约有NA个气体分子

D.25℃时,l L pH=13的Ba(OH)2溶液中含 Ba2+的数目为0.1NA

答案

答案:C

题目分析:氦元素是0族元素,具有稳定电子层结构,因此氦气分子是单原子分子,则1mol氦气分子含有1mol氦原子,故A错误;0℃、101kPa就是标准状况,由于Vm=22.4L/mol、n=V/Vm,则n(H2)=1mol,氢气分子是双原子分子,则1mol氢气分子含有2mol氢原子,故B错误;混合气体的物质的量也可以用n=V/Vm计算,则空气中各种分子总物质的量为1mol,1mol混合气体含有NA个气体分子,故C正确;25℃时溶液中Kw =10-14, c(H+)=10-pHmol/L,c(OH)=Kw/ c(H+)=10-1mol/L,由于n=c•V,则n(OH)= 10-1mol/L×1L=0.1mol,由于Ba(OH)2是强电解质,Ba(OH)2=Ba2++2OH中各物质的系数之比等于物质的量之比,则n(Ba2+)= n(OH)/2=0.05mol,故D错误。

问答题 简答题
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