Question

（2012?溧水縣二模）某硝酸銨（NH₄NO₃）樣品（雜質(zhì)不含氮）中氮元素的質(zhì)量分數(shù)為24.5%，則其中硝酸銨的質(zhì)量分數(shù)是（　�。�

A．20%

B．70%

C．80%

D．無法計算

Answer 1

分析：先計算出純凈硝酸銨中氮元素的質(zhì)量分數(shù)，再計算樣品中NH₄NO₃的質(zhì)量分數(shù)；根據(jù)混合物中某化合物的質(zhì)量分數(shù)=

含雜質(zhì)物質(zhì)元素的質(zhì)量分數(shù)

物質(zhì)中某元素的質(zhì)量分數(shù)

×100%，進行分析解答．

解答：解：純凈硝酸銨中氮元素的質(zhì)量分數(shù)=

14×2

14+1×4+14+16×3

××100%=35%，
硝酸銨（NH₄NO₃）樣品樣品中NH₄NO₃的質(zhì)量分數(shù)為：

24.5%

35%

×100%=70%．
故選B．

點評：本題有一定難度，掌握混合物中某化合物的質(zhì)量分數(shù)=

含雜質(zhì)物質(zhì)元素的質(zhì)量分數(shù)

物質(zhì)中某元素的質(zhì)量分數(shù)

×100%即可正確解答本題．