Final answer:
Applying Boyle's Law, the volume of the balloon at a higher altitude with a pressure of 0.25 atm, while maintaining constant temperature, would be 80.0 mL. The initial conditions were a volume of 20.0 mL at a standard pressure of 1 atm.
Step-by-step explanation:
The student's question involves the behavior of a gas under different pressures, assuming that the temperature remains constant. This concept is governed by Boyle's Law, which states that the volume of a fixed amount of gas held at a constant temperature varies inversely with the pressure. Using Boyle's Law, we can determine the new volume of the balloon when the pressure changes.
Given that the initial volume (V1) of the gas is 20.0 mL at an initial pressure (P1) of 1 atm, and the final pressure (P2) is 0.25 atm, we can set up the equation P1V1 = P2V2. Plugging in the known values:
1 atm × 20.0 mL = 0.25 atm × V2
Solving for V2, we get:
V2 = (1 atm × 20.0 mL) / 0.25 atm
V2 = 80.0 mL
Therefore, the volume of the balloon at the higher altitude where the air pressure is only 0.25 atm would be 80.0 mL.