[Win,odd Dhamnekar]

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

My answer:

Mass of C=Mass of CO₂*12/44
3.703*12/44=1.010
% C=1.010/2.036*100=49.61%

Mass of H=Mass of H₂O*2/18
1.526*2/18=0.1696
% H=0.1696/2.036*100=8.330%

The next element is determined similarly, using the second sample.
Mass of S=Mass of BaSO₄*32.06/233.6
3.236*32.06/233.6=0.4433
% S=0.4433/3.694*100=12.00%

The final element is obtained by difference.
%Br=100-(49.61+8.330+12.00)=30.06%