At a temperature of 27 ° C, the gas pressure in the closed vessel was 80 kPa. what will the pressure be at a temperature of -20 C.

To calculate the pressure of a given gas after cooling (isochoric process (closed vessel)), we will use the proportion: P1 / T1 = P2 / T2 and P2 = P1 * T2 / T1.

Values of variables: Р1 – initial pressure in the vessel (Р1 = 80 kPa); T2 – considered temperature (Т2 = 253 К = -20 ºС); T1 – initial temperature (Т1 = 300 К = 27 ºС).

Let’s calculate: P2 = 80 * 253/300 = 67.47 kPa.

Answer: The pressure of the target gas at -20 ºС will be 67.47 kPa.