physics
posted by IsabelA .
A cylinder contains 3.5 L of oxygen at 350 K and 2.5 atm . The gas is heated, causing a piston in the cylinder to move outward. The heating causes the temperature to rise to 640 K and the volume of the cylinder to increase to 9.5 L.
What is the gas pressure?

Use the initial set of numbers and the ideal gas law to compute the number of moles, n.
n = PV/(RT)= 2.5*3.5/(0.0826*350)= 0.304 moles
I used R = 0.0826 liter*atm/(mole K)
Then use the ideal gas law again with the above value of n to solve for the unknown P.
P = nRT/V