设生成硫化亚铁的质量为x
Fe + S = FeS
56 32 88
4g x
32/88=4g/x x=11g
还有3克铁粉剩余,设生成氢气的质量为y
Fe + 2 HCl = H2 +FeCl2
56 2
3g y
56/2=3g/y y=0.1g