A large balloon contains 65.0 L of helium gas at 25 °C and a pressure of 745 mm Hg. The balloon ascends to 3000 m, at which the external pressure has decreased by 30.%. What would be the volume of the balloon, assuming it expands so that the internal and external pressures are equal? (Assume the temperature is still 25 °C.)

1 answer

If the temperature remains constant, then Boyles law applies:
PV=constant
Here
P1=745 mmHg
V1=65 L
P2=745(1-0.3)=521.5
V2=?

P1V1=P2V2
745*65=521.5*V2
Solve for V2.