A research team is evaluating the behavior of a helium-filled weather balloon as it…
CHEMISTRY · Multi-part · A Level · Chemistry · Amount of substance · Amount of substance
Problem
A research team is evaluating the behavior of a helium-filled weather balloon as it ascends through Earth’s atmosphere. On the launch pad the balloon occupies a volume of 25.0 L at an external pressure of 1.00 atm and a temperature of 298 K. During ascent the amount of helium remains constant while the atmospheric pressure and temperature both change.
Assume the balloon gas always remains in mechanical and thermal equilibrium with the surrounding air.
(a) Derive an algebraic expression for the ratio V1V2 in terms of the initial and final pressures (P1,P2) and temperatures (T1,T2) for a fixed quantity of gas in a flexible container.
(b) Given that both P2<P1 and T2<T1, explain qualitatively how these simultaneous changes compete to influence the balloon’s volume. Indicate which effect you predict will dominate for typical tropospheric conditions and justify your reasoning with the expression from part (a).
(c) If the external pressure continues to decrease while the temperature stabilizes at a constant value, describe qualitatively what will happen to the balloon’s volume and why. Include a statement about any limiting factors that might prevent indefinite volume expansion.