So, I made the mistake of accelerating chemistry in summer school, and now I'm stuck with these questions and I have no clue were to begin:

A flask contains 2 mol of nitrogen gas and 2 mol of helium gas. how many grams of argon must be pumped into the flask in order to make the partial pressure of argon twice that of helium?

for this question, right now I've assumed that volume is 1L (not sure if this is the way to do it) and grabbed the molar mass of helium, multiplied it by 2 mols and multiplied that by 2 to get the density (in g/L) of argon I need to get double of helium, but something tells me I'm not doing this right...

A sample gas at stp has a density of 2.16g/L. the sample is then transferred to a heating chamber at 150kPa. Its density changes to 0.72 g/L. what is the kelvin tempreature inside the chamber?

for this question, I am generally a bit clueless. I used gay lussac's law to get p1/t1 = p2/t2, which translates to 101.325kpa/273K = 150kpa/x kelvins, with x equating to 404.145k. however, I totally disregarded density, so I don't think this is the right approach either

also, thanks for your time and help. I'm desperate and this is due tomorrow.