Question

Carbon dioxide initially at 50 kPa, 400 K, undergoes a process in a closed system until its pressure and temperature are 2 MPa and 800 K, respectively. Assuming an ideal gas behaviour, find the entropy change of the carbon dioxide by assuming that the specific heats are constant. For the gas, take Cp = 0.846 kJ/kg.K and R = 0.1889 kJ/kg.K

Answer 1

Answer:

$\Delta S=-0.11\frac{kJ}{kg*K}$

Explanation:

Hello,

In this case, we can compute the entropy change by using the following equation containing both pressure and temperature:

$\Delta S=Cp\ ln(\frac{T_2}{T_1} )-R\ ln(\frac{p_2}{p_1} )$

Thus, we use the given data to obtain (2 MPa = 2000 kPa):

$\Delta S=0.846\frac{kJ}{kg*K} \ ln(\frac{800K}{400K} )-0.1889\frac{kJ}{kg*K} \ ln(\frac{2000kPa}{50kPa} )\\\\\Delta S=-0.11\frac{kJ}{kg*K}$

Best regards.