100g*19.6%=19.6g
Zn + H2SO4 === ZnSO4 + H2↑
65 98 161 2
x 19.6g y z
65/x=98/19.6g=161/y=2/z
x=13g
y=32.2g
z=0.4g
可制得氢气的质量是0.4g
反应后所得溶液的浓度 32.2g/(13g+100g-0.4g)*100%=28.6%