Posted by Sarah on .
A 3.80 L cylinder contains 6.83 g of methane, CH4, at a pressure of 3320 mmHg. What is the temp. Of the gas?
I mainly have problems being able to tell which gas law equation I need to use when asked these types of questions and then being able to rearrange the equation to find my answer that I need. If there an easy way to do this or to be able to tell?
Thank you.

Chemistry 
DrBob222,
If you have two sets of conditions, the easy gas law to use is the
(P1V1/T1) = (P2V2/T2)
If you don't have two sets of data you almost certainly must use PV = nRT. Many times, and this problem is one of them, the problem gives grams so you calculate mols = n = grams/molar mass.
Also,if you mean by "rearranging the equation to find my answer" as rearranging the equation FIRST, I wouldn't do that. I would substitute into the equation you want (either of the two equations above), then rearrange the numbers to solve for the unknown.
For this problem you want PV = nRT.
P must be in atm (mmHg/760), n = mols = grams/molar mass, when you solve for T the answer will be in kelvin.