Specific heat at constant pressure,
$$${C_p} = 1.005\,\,kJ/kg\,\,K;$$$

Specific heat at constant volume,
$$${C_v} = 0.718\,\,kJ/kg\,\,K;$$$

Characteristic gas constant, $$R=0.287$$ $$kJ/kgK.$$

Enthalpy $$h = {C_p}T,$$

Internal energy, $$u = {C_v}T.$$

If the air has to flow from station $$P$$ to station $$Q,$$ the maximum possible value of pressure in $$kPa$$ at station $$Q$$ is close to

Specific heat at constant pressure,
$$${C_p} = 1.005\,\,kJ/kg\,\,K;$$$

Specific heat at constant volume,
$$${C_v} = 0.718\,\,kJ/kg\,\,K;$$$

Characteristic gas constant, $$R=0.287$$ $$kJ/kgK.$$

Enthalpy $$h = {C_p}T,$$

Internal energy, $$u = {C_v}T.$$

If the pressure at station $$Q$$ is $$50$$ $$kPa,$$ the change in entropy $$\left( {{S_Q} - {S_p}} \right)$$ in $$kJ/kgK$$ is