MA=15.2=30 gam

nC=nCO2=0,6644=0,015molnC=nCO2=0,6644=0,015mol→→mC=0,015.12=0,18 gam

nH=2nH2O=20,2718=0,03molnH=2nH2O=20,2718=0,03mol→→mH=0,03 gam

mO=0,45-(0,18+0,03)=0,24gam→→nO=0,2416=0,015mol0,2416=0,015mol

%C=0,18.1000,45=40%0,18.1000,45=40%

%H=0,03.1000,45=6,67%0,03.1000,45=6,67%

%O=100%-40%-6,67%=53,33%

- Đặt CTPT: CxHyOz

- Tỉ lệ: x:y:z=0,015:0,03:0,015=1:2:1

→→Công thức nguyên: (CH2O)n

- Ta có: (12+2+16)n=30→→30n=30→→n=1

CTPT: CH2O