Gọi mCO2=44a
mH2O =15a
=> nCO2 = a mol
nH2O =5/6 a mol
=>nO = a+ 5/6a = nO(O2) + nO(X) => 11/6 a= 0,375 + nO(X) (1)
2,85 = mC + mH + mO = 12a + 5/3 a + 16*nO(X) (2)
(1), (2) => a=0,15 & nO(X) =0,05
=> nC : nH :nO = 3:5:1
=> CTDG nhat la C3H5O
=> CTPT la (C3H5O)n
M(X) = 3,8 *30=114 => n=2
=> CTPT la C6H10O2