Gas equations pressure volume energy

Question

A sample of helium gas occupies a volume of 0.50 L at a pressure of 0.95 atm. What volume will the gas occupy at a pressure of 1.50 atm if the temperature remains constant?

Answer 1

Hello, Jacob,

J.R. S. has answered this already, but I'll add one tip for future problems. In this case, the temperature was held constant, so we don't need to address it in the calculations here. But many situations will have temperature changes and it is helpful to remember the overall equation for gas law problems (in which the moles of gas stay the same - nothing added or removed).

This equation is easy to remember once you say it aloud a few times: "P1V1 over T1 is equal to P2V2 over T2." Remember that temperatures for the gas laws must be Kelvin (dividing by 0^oC would disturb the mathematicians).

This equation is valid as long as the moles of gas stay the same. You'll note that this is what J.R. S. has done in answering your problem. Since there is no temperature change, T1 = T2, and temperature cancels out, leaving the equation that J.R. S. uses.

By setting up a table of the knowns, just as was done, it becomes easier, and safer, to input the correct values.

Always check to see that the units are consistent, and cancel to what you want/expect.

Bob

Answer 2

V1 = Initial Volume = 0.50 L

P1 = Initial Pressure = 0.95 atm

V2 = Final Volume = ?

P2 = Final Pressure = 1.50 atm

Use Boyles Law:

P1V1 = P2V2 and solve for V2

P1V1/P2 = V2

V2 = (0.95 atm)(0.50 L) / (1.50 atm)

V2 = 0.32 L