Предмет: Химия, автор: munekotun

срочно!
В школьной лаборатории ученики приготовили 20% раствор хлорида цинка
массой 200 г и ставили его на лето в бутылке с незакрытой крышкой. К
сентябрю раствор стал весить 160 г. Какая массовая доля раствора стала к
осени?
w(p-paZnClg2) =?%

Ответы

Автор ответа: chemistrykk

Дано:

w1(ZnCl2) = 20%= 0,2

m1(р-ра ZnCl2) = 200 г

m2(р-рв ZnCl2) = 160 г

Найти:

w2(ZnCl2) - ?

Решение:

m(в-ва)=w×m(р-ра)

m(ZnCl2) =0,2 × 200 = 40 г

Масса вещества не меняется, значит:

w=m(в-ва)/m(р-ра)×100%

w2(ZnCl2) = 40/160×100% = 25%

Ответ: 25%

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