First, assume ideal gas behavior for simplicity. To simplify even further, let's use the formula for special cases. In cases where the system is at constant volume,we will use the Gay-Lussac's Law written below:
P₁/T₁ = P₂/T₂
Note that T should be absolute. Let's solve for T₂.
1 atm/25+273 K = 0.5 atm/T₂+273 K
Solving for T₂,
T₂ = 124°C
