I suspect that the pressure of this change is constant therefore
The equation is used from the combined gas law. (When pressure is constant both P's will cancel out P/P = 1)
V/T = V/T
Initial Change
Initially we have 2L at 20 degress what temperature will be at 1L.
2/20 = 1/T
0.1 = 1/T
0.1T = 1
T = 1/0.1
T = 10 degress celsius.
Hope this helps if you won't be able to understand what is the combined gas law just tell me :).
