Combining Gases and Pressure?

Question

Gaseous Mixture has 6.91g of N2, 4.71g of O2, and 2.95g of He. What volume does this mixture occupy @ 28C and 1.05 atm pressure? Please show me how you got this answer. I am thinking I need to convert the grams to moles? Thank you!

I came up with .49 mol of N2, .29 mol of O2 and .74 mol of He. Total equals 1.52 mol is this correct? My answer doesn't match the back of the book. please advise,

Answer 1

Any ideal gas calculation requires moles. So do your grams to mole conversions. Then add up the moles and do the PV= nRT thing with T=301 K and R as 0.082 Lit-Atm/degK-mole