Question

蓄電池中所用的電解液是濃度為28%的硫酸，若用1升98%的濃硫酸（密度為1.98g/cm³）稀釋成28%的硫酸，則需要加水    升．

Answer 1

【答案】分析：用濃溶液加水稀釋成稀溶液，在加水的過程中溶質(zhì)的質(zhì)量不變，即濃溶液的質(zhì)量×濃溶液中溶質(zhì)的質(zhì)量分?jǐn)?shù)=稀溶液質(zhì)量×稀溶液中溶質(zhì)的質(zhì)量分?jǐn)?shù)．
解答：解：由于在加水稀釋過程中溶質(zhì)的質(zhì)量不變，1L=1000cm³，濃溶液的質(zhì)量為1000cm³×1.98g/cm³=1980g，濃溶液中溶質(zhì)的質(zhì)量也就是稀溶液中溶質(zhì)的質(zhì)量為1980g×98%=1940.4g，則稀溶液的質(zhì)量為=6930g，溶液由1980g變成了6930g，增加了4950g，即加入水的質(zhì)量為4950g，則需要加水的體積為=4950mL=4.95L．
故答案為：4.95
點(diǎn)評(píng)：本題的難度較大，主要考查了用水稀釋溶液的過程中溶質(zhì)質(zhì)量不變的有關(guān)溶質(zhì)質(zhì)量分?jǐn)?shù)的簡單計(jì)算，從而加深學(xué)生對(duì)溶質(zhì)質(zhì)量分?jǐn)?shù)概念的理解，培養(yǎng)學(xué)生的計(jì)算能力和解決問題的能力．