materials question?

Question

High-density polyethylene may be chlorinated by inducing the random substitution of chlorine atoms for hydrogen.

Determine the weight percent of Cl that must be added if this substitution occurs for 4% of all the original hydrogen atoms.

Express your answer with one decimal digit.

thanks, working out plz

Answer 1

High-density polyethylene can be considered with -(CH2)- structure, thus has a C-H weight ratio of 12.011:2*1.00794. The weight percent of H is: 2*1.00794/(12.011+2*1.00794) x 100%.
if this substitution occurs for 4% of all the original hydrogen atoms, the weight percent of Cl is:
8%*35.453/(12.011 + 192%*1.00794 + 8%*35.453)
= 0.169
= 16.9%