(2002?呼和浩特)某同學(xué)在t℃時(shí)用100g硝酸鉀溶液做結(jié)晶實(shí)驗(yàn).他先將溶液蒸發(fā)掉20g水,冷卻至t℃得到8g晶體(晶體不含結(jié)晶水);然后繼續(xù)蒸發(fā)掉10g水,冷卻至t℃,又得到6g晶體.則該同學(xué)所取原溶液中溶質(zhì)的質(zhì)量分?jǐn)?shù)為( ?。?br/>A. 14%
B. 35%
C. 37.5%
D. 60%
根據(jù)題意,t℃時(shí)硝酸鉀的溶解度=
×100g=60g,則蒸發(fā)掉20g水,冷卻至t℃得到8g晶體后所余(100g-20g-8g)即72g硝酸鉀飽和溶液中硝酸鉀的質(zhì)量=
×100%×72g=27g,
則所取原溶液中溶質(zhì)的質(zhì)量分?jǐn)?shù)=
×100%=35%
故選B.