Question

You place a newly discovered gas into a 2.00 liter container. The pressure of the gas is 0.500 atm at 20.0oC. You heat the gas to 30.0oC by adding 50.1 Joules of energy to the gas. What is the value of Cp bar of the gas?

Answer 1

Cpbar is the molar heat capacity

molar heat capacity is defined as the quantity of heat required to raise the temperature of one mole of gas by 1C at constant pressure.

i) calculating number of moles of gas in container

From ideal gas equation PV = nRT

number of moles gas n = PV/RT

= 0.500atm x 2.00L /0.0821 L.atm/mol.K x 293K

= 0.04157 mol

ii) to heat 0.04157mol of gas by 10C heat used = 50.1 J

so raise by 1 C the heat required = 5.01 J

thus to rise the temperature by 1C for 0.04157 mol of gas 5.01 J is required

to rise the temperaature by 1C for one mole of gas = 1mol x 5.01J /0.04157

= 120.52 J

Thus Cp bar of gas = 120.52 J/K