Chemistry
posted by Angie .
I need help with part b here's all information.
(a) Chlorine gas is added to a glass cylinder of 2.5 cm in radius, fitted with a movable piston. Gas is added until the piston is lifted 5 cm off the bottom of the glass. The pressure on the gas is 1 atm, and the gas and cylinder are at room temperature 25C. How many moles of chlorine were added to the cylinder?
My answer was 0.0040128 moles which is correct.
Part B I need help.
(b) Pressure is applied to the piston, compressing the gas until the piston is 2 cm from the bottom of the cylinder. When the temperature returns to 25C, what is the pressure in the cylinder (in atm)? Assume that chlorine behaves as an ideal gas under these conditions. The molecular weight of chlorine is 70.9 g/mol.

You used PV = nRT to arrive at n for part a.
For part b, recalculate the volume. It is
pi*r^2*h = 3.14*(2.5^2)(5) = ?cc and convert to L.
Then p = nRT/V and solve for p. 
In part b when it says compressing the piston 2 cm from the bottom of the cylinder. This value is irrelevant?

No it is relevant. In my response I wrote 5 for h; I should have written 2 for h. If I punched in the numbers right that should be a volume of 39.27 cc or 0.03927 L. Check me out on that. Let me know if you don't get the right answer.