How to do this chemistry problem with gases?

Chemistry Problem-Gases?

• A spherical glass container of unknown volume contains helium gas at 25 C and 1.960 atm. When a portion of the helium is withdrawn and adjusted to 1.00 atm and 25 C, it is found to have a volume of 1.75 cm^3. The gas remaining in the first container shows a pressure of 1.710 atm. Calculate the volume of the spherical container.

• Answer:

  Assuming the temperature of the original container didn't change when the second pressure measurement was made and assuming Helium behaves like an ideal gas we can solve this with the ideal gas law. PV=nRT 1.00 atm x 0.00175 L=n x 0.0821(atm*L)/(mol*K) x 298 K n=7.15284x10^-5 mol He alright so that's how much He was removed from the first container. The change in number of moles is directly proportional to the change in pressure. θP=1.960 atm-1.710 atm=0.25 atm 0.25 atm/1.960 atm=7.15284x10^-5 mol/n1 n1=5.608x10^-4 mol PV=nRT 1.960 atm x V=5.608x10^-4 mol x 0.0821(atm*L)/(mol*k) x 298 K V=0.007 L= 7 cm³