Gas law problem help!?

1in a study of o2, a scientist prepares an atmosphere consisting of 79% N2 & 21% o2. the total pressure is 5.68 atm. calculate the partial pressure of the o2-------#2 a 57.8 moles of a Cl2 sample of gas fills a container with 47.3 mL. 13.5 additional grams of Cl2 were dropped in the container. what is the adjusted volume??