mO2= 3,36/2,24 .32= 4,8g
=> mH2O, CO2= 2,5+4,8= 7,3g
=> mCO2+ mH2O= 7,3g (1)
Mà mCO2- mH2O= 3,7g (2)
(1)(2) giải hệ: mCO2= 5,5g; mH2O= 1,8g
nC= nCO2= 5,5/44= 0,125 mol => mC= 1,5g
nH= 2nH2O= 2. 1,8/18= 0,2 mol => mH= 0,2g
=> mO= 2,5-1,5-0,2= 0,8g
%C= 1,5.100:2,5= 60%
%H= 0,2.100:2,5= 8%
%O= 32%