燃烧方程式：若为烷烃,CxH(2x+2)+(1.5x+0.5)O2=xCO2+(x+1)H2O,
10ml烃燃烧后体积减小20ml,对应的1+1.5x+0.5-x=2,x=1,是甲烷CH4
同理,烯烃是C2H4,炔烃是C3H4