Question

The question has been answered years ago but not how it is solved. I tried the combined gas law. Here is the question: A balloon originally had a volume of 4.39 L at 44 degrees celsius and a pressure of 729 torr. The balloon must be cooled ??? to reduce its volume to 3.78 L at constant pressure.
I used T2= P2*V2*T1/ P1*V1
Please help me understand why it is zero degrees!

Answer 1

First since it is constant P you don't need the P1 and P2 so the equation can be modified to T2 = V2T1/T2 although you could use your formula and just use 729 for P1 and 729 for P2.

V2 is 3.78L
V1 is 4.39L
T1 is 44 C which is (273+44) = 317 Kelvin.

Substitute into the equation for
3.78*317/4.39 = 272.95K and that rounds to 273 K. To convert to C, that is
K = 273+C or 273-273 = zero Celsius.