I need help

[yusufhamood]

1)At what temperature wil 0.2g of helium exert a pressure of 80kPa in a container with a fixed volume of 2.0

2)A sample of gas of mass 10.0g occupies a volume of 5.4l at 27 degrees C and 100 x 10^3 Pa
Calculate the amount in mol of gas in sample
Determine the molar mass of gas

[Srd2000]

1) Whenever you have a mass of stuff, find the number of moles of said stuff.
Then from there you have the majority of the components needed for your universal gas equation; PV=nRT. Where P is the pressure in kPa, V is the volume in L, n is the number of moles in mol, R is the gas constant 8.31 J/mol K and T is your temperature in K.
Simply plug in the values for the corresponding symbol and solve for your unknown value, T.

2) Basically the same question as the above one, except you are working backwards.
Chuck everything into PV=nRT that you know and solve for what you don't know, number of moles. Part a is done.
What is a mole equal to? The mass of stuff divided by the molar mass of the stuff. Look at it, you'll have the number of moles from part a and you're given the mass of stuff, solve for what you don't know. This will give you the molar mass of the gas. Done


Hope this helps