反应前后固体质量差 = 1-0.75 = 0.25g
4FeS2 +11O2 ==点燃== 2Fe2O3 + 8SO2 △m
480 160
m 0.25g
480/m = 160/0.25g
m = 0.75g
FeS2质量分数 = 0.75/1 = 75%