An ideal gas in a sealed container has an initial volume of 2.55 l. at constant pressure, it is cooled to 18.00 °c where its final volume is 1.75 l. what was the initial temperature?

Data Given:
                   V₁  =  2.55 L

                   T₁  =  ?

                   V₂  =  1.75 L

                   T₂  =  18 °C + 273.15  =  291.15 K

Solution:
             Let suppose the Gas is acting Ideally, Then According to Charle's Law,
                              P₁ / T₁  =  P₂ / T₂
Solving for T₁,
                              T₁  =  V₁ × T₂ / V₂
Putting Values,
                              T₁  =  (2.55 L × 291.15 K) ÷ 1.75 L

                              T₁  =  424.24 K
Or,
                              T₁  =  151 °C