A certain flexible weather balloon contains helium gas at a volume of 855 L. Initially, the balloon is at sea level where the temperature is 25°C and the barometric pressure is 729 torr.

Question

The balloon then rises to an altitude of 6000 ft, where the pressure is 605 torr and the temperature is 15°C. What is the change in volume of the balloon (in L) as it ascends from sea level to 6000 ft?

Answer 1

This is a straightforward application of the Gas Laws:

P(1)V(1)/T(1) = P(2)V(2)/T(2), where

P(1) = 729 torr

V(1) = 855 L

T(1) = 298 deg K (25 deg C + 273)

P(2) = 605 torr

V(2) = TBD

T(2) = 288 deg K

Solve for V(2) and subtract V(1) from it to find the change in volume. V(2) will be larger that V(1), so the change will be positive. Around 150 L