Question

73.5 grams C, 4.20 grams H, and 72.3 grams Cl. What is the percent composition of each element in this compound?

Answer 1

To find percent composition do "parts over the whole" ---> each individual mass over the total mass times 100 (since it is a percentage). 

total mass ("the whole")= 73.5 + 42.0 + 72.3 grams= 150 grams

1. Carbon %= 73.5 grams/ 150 grams x 100= 49.0%

2. Hydrogen %= 4.20 grams/ 150 grams x 100= 2.80%

3. Chlorine %= 72.3 grams/ 150 grams x 100= 48.2%