# The cylinder contains compressed oxygen at a temperature of 25 degrees Celsius and a pressure

**The cylinder contains compressed oxygen at a temperature of 25 degrees Celsius and a pressure of 1.5 * 10 ^ 7 Pa. in the process of gas welding, half of the oxygen is consumed. Determine what pressure will be established in the cylinder if the gas temperature has dropped to 15 degrees Celsius.**

Let’s convert the temperature from Celsius to Kelvin:

T1 = 25 ° C = 298 K;

T2 = 15 ° C = 288 K;

For the calculation, we will use the Mendeleev-Clapeyron equation:

PV = nRT, where

n is the amount of gas substance, mol;

R – universal gas constant, 8.314 J / mol;

T is temperature, K;

Р – pressure, Pa;

V – volume, m3;

P = nRT / V;

n2 = 0.5 n1;

V = const;

P2 / P1 = (n ^ 2 * R * T ^ 2 / V): (n1 * R * T1 / V) = (0.5 * n1 * T ^ 2) / (n1 * T ^ 2) = (0 .5 * 288) / 298 = 0.48

P2 = 1.5 * 10 ^ 7 * 0.48 = 7.2 * 10 ^ 6 Pa.

Answer: P2 = 7.2 * 10 ^ 6 Pa.