Fe + 2HCl = FeCl2 + H2(g)
56 2
x 0.2
56 :2 = x :0.2
x = 5.6 g
合金中铁的质量分数:5.6/10 = 56%
用物质的量更快
0.2g=0.1molH2=0.1molFe=5.6g
所以为56%
希望明白