Question

17．計(jì)算80g質(zhì)量分?jǐn)?shù)為15%的NaNO₃溶液里含有溶質(zhì)的質(zhì)量？向以上所說的溶液中加入20g水后所得溶液中溶質(zhì)的質(zhì)量分?jǐn)?shù)是多少？如向原溶液中加入20g NaNO₃并使之完全溶解，求所得溶液中溶質(zhì)的質(zhì)量分?jǐn)?shù)是多少？

Answer 1

分析 根據(jù)溶質(zhì)質(zhì)量=溶液質(zhì)量×溶質(zhì)的質(zhì)量分?jǐn)?shù)，溶質(zhì)質(zhì)量分?jǐn)?shù)=$\frac{溶質(zhì)質(zhì)量}{溶液質(zhì)量}$×100%，進(jìn)行分析解答即可．

解答 解：80g質(zhì)量分?jǐn)?shù)為15%的NaNO₃溶液里含有溶質(zhì)的質(zhì)量是：80g×15%=12g；
溶液中加入20g水后所得溶液中溶質(zhì)的質(zhì)量分?jǐn)?shù)是：$\frac{12g}{80g+20g}×100%$=12%；
向原溶液中加入20g NaNO₃并使之完全溶解，求所得溶液中溶質(zhì)的質(zhì)量分?jǐn)?shù)是
在80g質(zhì)量分?jǐn)?shù)為15%的KNO₃溶液里加入20g KNO₃后完全溶解，所得溶液中溶質(zhì)的質(zhì)量分?jǐn)?shù)是$\frac{12g+20g}{80g+20g}$×100%=32%．
答：80g質(zhì)量分?jǐn)?shù)為15%的NaNO₃溶液里含有溶質(zhì)的質(zhì)量是12g，向以上所說的溶液中加入20g水后所得溶液中溶質(zhì)的質(zhì)量分?jǐn)?shù)12%，如向原溶液中加入20g NaNO₃并使之完全溶解，所得溶液中溶質(zhì)的質(zhì)量分?jǐn)?shù)是32%．

點(diǎn)評 本題難度不大，掌握溶質(zhì)質(zhì)量=溶液質(zhì)量×溶質(zhì)的質(zhì)量分?jǐn)?shù)、溶質(zhì)質(zhì)量分?jǐn)?shù)=$\frac{溶質(zhì)質(zhì)量}{溶液質(zhì)量}$×100%是正確解答本題的關(guān)鍵．