Question

A balloon is filled with 3.00 l of helium at a pressure of 765 torr. what is the volume (l) of the balloon at an altitude where the pressure in the balloon is 70,661 pa?

Answer 1

We assume ideal gas behaviour so we can use the formula:

PV = nRT

From the problem, we can say that the amount of Helium does not change so n is constant and that we assume no change in temperature so that T is also constant, therefore:

P V = constant

And then:

P1 V1 = P2 V2

765 torr * 3.00 L = 70,661 Pa (760 torr / 101325 Pa) * V2

V2 = 4.33 L