溶液的稀釋和增濃問(wèn)題

(1)關(guān)于溶液的稀釋計(jì)算：因?yàn)橄♂屒昂笕苜|(zhì)的質(zhì)量不變，所以若設(shè)濃溶液質(zhì)量為Ag，溶質(zhì)的質(zhì)量分?jǐn)?shù)為a%，加水稀釋成溶質(zhì)質(zhì)量分?jǐn)?shù)為b%的稀溶液Bg，則Ag×a%=Bg×b%其中B=A+m水

(2)溶液增濃的計(jì)算

①向原溶液中添加溶質(zhì)：設(shè)原溶液質(zhì)量為Ag，溶質(zhì)的質(zhì)量分?jǐn)?shù)為a%，加溶質(zhì)Bg后變成溶質(zhì)質(zhì)量分?jǐn)?shù)為b%溶液，則Ag×a%+Bg=(Ag+Bg)×b%

②將原溶液蒸發(fā)掉部分溶劑：因?yàn)槿芤赫舭l(fā)溶劑前后，溶質(zhì)的質(zhì)量不變。所以若設(shè)原溶液質(zhì)量為Ag，溶質(zhì)的質(zhì)量分?jǐn)?shù)為a%，蒸發(fā)Bg水后變成溶質(zhì)質(zhì)量分?jǐn)?shù)為b%溶液，則

Ag×a%=(Ag-Bg)×b%

③與濃溶液混合：因?yàn)榛旌衔锶芤旱目傎|(zhì)量等于兩混合組分溶液的質(zhì)量之和。混合后的溶液中溶質(zhì)的質(zhì)量等于兩混合組分的溶質(zhì)質(zhì)量之和。所以設(shè)原溶液質(zhì)量為Ag，溶質(zhì)的質(zhì)量分?jǐn)?shù)為a%，濃溶液的質(zhì)量為Bg，溶質(zhì)質(zhì)量分?jǐn)?shù)為b%，兩溶液混合后得到溶質(zhì)的質(zhì)量分?jǐn)?shù)為c%的溶液，則Ag×a%+Bg×b%=(Ag+Bg)×c%

注意

溶液的質(zhì)量和體積換算：密度=質(zhì)量/體積

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