Final answer:
The volume of the weather balloon at -15.5 °C assuming pressure is held constant is approximately 18.81 L.
Step-by-step explanation:
To find the volume of the weather balloon at -15.5 °C assuming pressure is held constant, we can use the combined gas law equation: P1*V1/T1 = P2*V2/T2. Given that the initial temperature is 0.00 °C and the initial volume is 20.0 L, and the final temperature is -15.5 °C, we can plug in the values to find the final volume:
P1*V1/T1 = P2*V2/T2
0.00 * 20.0 / 273.15 = P2 * V2 / (273.15 - 15.5)
Solving for V2, we get:
V2 = (0.00 * 20.0 / 273.15) * (273.15 - 15.5)
V2 ≈ 18.81 L