Question

A 2.80 -g sample of an unknown chlorofluorocarbon is decomposed and produces 557mL of chlorine gas at a pressure of 750mm Hg and a temperature of 298K .

What is the percent chlorine (by mass) in the unknown chlorofluorocarbon?

Answer 1

Use the ideal gas law to find the moles of chlorine gas Cl2 :

n=PV/RT

then, change the moles to mass using the mole mass of Cl2

finally, percentCl is mass/2.80g