解：
設(shè)?$50\ \mathrm {kg }$?碳酸氫銨化肥中至少含有純凈的?$NH_{4}HCO_{3}$?的質(zhì)量為?$x。$?
?$NH_{4}HCO_{3}$?中氮元素的質(zhì)量分?jǐn)?shù)?$=\frac {14}{14+1×5+12+16×3}×100\%=\frac {14}{79}×100\%$?
已知化肥含氮量?$ 16.0\%，$?則?$x×\frac {14}{79}×100\%=50\ \mathrm {kg}×16.0\%$?
?$x=\frac {50\ \mathrm {kg}×16.0\%×79}{14}≈45.1\ \mathrm {kg}$?
答：?$50\ \mathrm {kg }$?碳酸氫銨化肥中至少含有純凈的?$NH_{4}HCO_{3}$?的質(zhì)量約為?$45.1\ \mathrm {kg}。$?
