This question presents analytical data from which you are required to determine mass % composition for a compound of up to four elements.
A sample of a compound containing C,H,S and Br is subjected to combustion analysis to determine the quantities of C and H present. Using a second sample, the S is analyzed by converting it to BaSO4. The results of the analysis are shown below.
Sample 1 Mass:2.036 ⇒ CO2 Mass:3.703 ; H2O Mass:1.526
Sample 2 Mass:3.694 ⇒ BaSO4:3.236
Mass of C=Mass of CO2*12/44
Mass of H=Mass of H2O*2/18
The next element is determined similarly, using the second sample.
Mass of S=Mass of BaSO4*32.06/233.6
The final element is obtained by difference.