In a separate experiment beginning from the same initial conditions, including a temperature Ti of 25.0°C, half the number of moles found in part (a) are withdrawn while the temperature is allowed to vary and the pressure undergoes the same change from 25.7 atm to 4.10 atm. What is the final temperature (in °C) of the gas?

- 178 ºC

Explanation:

The ideal gas law states that:

PV = nRT,

where P is the pressure, V is the volume, n is number of moles, R is the gas constant and T is the absolute temperature.

For the initial conditions:

P₁ V₁ = n₁ R T₁ (1)

and for the final conditions:

P₂V₂ = n₂ R T₂ where n₂ = n₁/2 then P₂ V₂ = n₁/2 T₂ (2)

Assuming V₂ = V₁ and dividing (2) by Eqn (1):

P₂ V₂ = n₁/2 R T₂ / (n₁ R T₁) then P₂ / P₁ = 1/2 T₂ / T₁

4.10 atm / 25.7 atm = 1/2 T₂ / 298 K ⇒ T₂ = 0.16 x 298 x 2 = 95.1 K

T₂ = 95 - 273 = - 178 º C