Question

把7克含雜質(zhì)的鋅片（雜質(zhì)不與鹽酸反應(yīng)）投入100克足量的稀鹽酸里，反應(yīng)停止后所得混合物的總質(zhì)量為106.8克．（1）反應(yīng)后生成氫氣的質(zhì)量；（2）不純的鋅片中單質(zhì)鋅的質(zhì)量分?jǐn)?shù)．

Answer 1

反應(yīng)前后物質(zhì)的質(zhì)量差即放出氫氣的質(zhì)量=100g+7g-106.8g=0.2g
設(shè)生成0.2g氫氣需要鋅的質(zhì)量為x
Zn+2HCl=ZnCl₂+H₂↑
65            2
x           0.2g

65

x

=

2

0.2g

 
解之得 x=6.5g
不純的鋅片中單質(zhì)鋅的質(zhì)量分?jǐn)?shù)=

6.5g

7g

×100%≈92.9%
答：（1）反應(yīng)后生成氫氣的質(zhì)量為0.2g；（2）不純的鋅片中單質(zhì)鋅的質(zhì)量分?jǐn)?shù)為92.9%．