Combustion analysis of an unknown compound provides the following data: 73.5 grams C, 4.20 grams H, and 72.3 grams Cl. What is the percent composition of each element in this compound?
a. 73.5% C, 4.20% H, 72.3% Cl
b.48.0% C, 3.00% H, 50.0% Cl
c. 17.5% C, 1.00% H, 17.2% Cl
d. 49.0% C, 2.80% H, 48.2% Cl

Question

Combustion analysis of an unknown compound provides the following data: 73.5 grams C, 4.20 grams H, and 72.3 grams Cl. What is the percent composition of each element in this compound?  
    a. 73.5% C, 4.20% H, 72.3% Cl 
   b.48.0% C, 3.00% H, 50.0% Cl  
   c. 17.5% C, 1.00% H, 17.2% Cl 
  d. 49.0% C, 2.80% H, 48.2% Cl

anonymous · Answer

ok firs divide each mass with matching atomic mass:
73,5 g / 12,011 =6,12
4,2 g / 1,008 = 4,16
72,3 g / 35,45 = 2,04
so now you know it is dichlor benzene:
|dw:1338559170202:dw|
now by doing same steps as in last task calculate percentages.