Question

Find the values of Cp and ᵞ for a gas whose gas

constant is 0.324 kJ/kg K and Cv = 0 84 kJ/kg K.

If 2.25 kg of this gas with an initial volume of

1.15 m3 undergoes a process during which its

pressure remains constant at 7 bar and its

temperature becomes 280‘C at the end of the

process, calculate: (a) the change in internal

energy, (b) the change in enthalpy, (c) the

transferred heat, and (d) the work done.

Answer 1

Internal energy

$$U=mC_v∆T \\U=2.25\times0.84\times553=1045.17KJ$$

Enthalpy

$1bar=10^5 pa$

$$H=U+PV \\H=1045.17+7\times10^5\times1.15 \\H=1045.17+805\\H=1850.17KJ$$

Work done (W)=PdV

W=$7\times10^5\times1.15=805KJ$