设收集的NO2为Xml
(1)NO2过量
4NO2+O2+2H2O===4HNO3
4-----1
x----(1/4)x
则NO2完全反应,所以x+(1/4)x=90-40
得x=40ml
(2)NO2不足
3NO2+H2O===2HNO3+NO
3-------------------------1
x-----------------------(1/3)x
4NO+3O2+2H2O===4HNO3
空气为90-xml
O2为1/5(90-x)ml
4NO--------------3O2
4----------------3
4/15(90-x)-----1/5(90-x)
剩余气体为NO和N2
1/3x-4/15(90-x)+4/5(90-x)=40
解得:x=40