设混合物中含锌的物质的量为x、含铁的物质的量为y
则有:65g/mol × x + 56g/mol × y =12.1g ----(1)
Zn + H2SO4=ZnSO4 + H2 ↑
1 1
x x
Fe+ H2SO4=FeSO4 + H2 ↑
1 1
y y
x + y = 4.48L ÷ 22.4L/mol=0.2mol --------(2)
联立(1)(2)解得
X=0.1mol Y=0.1mol
则混合物中铁的质量=0.1mol × 56g/mol=5.6g
混合物中铁的质量分数=5.6g ÷ 12.1g × 100%=46.3%
答：混合物中铁的质量分数为46.3%