Question

3．向150克溶質(zhì)質(zhì)量分?jǐn)?shù)為10%的蔗糖溶液中加入5克蔗糖后的質(zhì)量分?jǐn)?shù)是多少？

Answer 1

分析 向150克溶質(zhì)質(zhì)量分?jǐn)?shù)為10%的蔗糖溶液中加入30克水后，溶質(zhì)的質(zhì)量發(fā)生改變，溶液質(zhì)量也隨著改變，利用溶液中溶質(zhì)質(zhì)量分?jǐn)?shù)的定義，溶液中溶質(zhì)的質(zhì)量分?jǐn)?shù)=$\frac{溶質(zhì)的質(zhì)量}{溶液的質(zhì)量}$×100%，計(jì)算該溶液中溶質(zhì)的質(zhì)量分?jǐn)?shù)．

解答 解：加水后溶液的溶質(zhì)質(zhì)量分?jǐn)?shù)=$\frac{150g×10%+5g}{150g+5g}×100%$=12.9%
答：向150克溶質(zhì)質(zhì)量分?jǐn)?shù)為10%的蔗糖溶液中加入30克水后的質(zhì)量分?jǐn)?shù)是12.9%．

點(diǎn)評(píng) 不論什么時(shí)候要求溶液中溶質(zhì)的質(zhì)量分?jǐn)?shù)一定要從題目中找出溶質(zhì)的質(zhì)量、溶液的質(zhì)量．然后根據(jù)公式求出．是已知條件的直接用，未知的要根據(jù)題目中的數(shù)量關(guān)系求出．