Determine ,W , Q, and . The properties for liquid carbon tetrachloride at 1 bar and 0°C may be assumed independent of temperature: ? =

Question

Five kilograms of liquid carbon tetrachloride undergo a mechanically reversible, isobaric change of state at 1 bar during which the temperature changes from 0°C to 20°C.





What will be an ideal response?

Answer 1

For an isobaric process with a substance with constant coefficient of thermal expansion, the change in volume is given by



Integrating this over finite temperature gives



So, when the temperature increases by 20 degrees, the specific volume change is given by



The initial specific volume is

The final specific volume is then



So, the change in specific volume is , and the change in total volume is The work done is simply (the carbon tetrachloride does 7.65 J of work on its surroundings when it expands by

The heat required is (more than 1000 times greater than the work done). The enthalpy change for the constant pressure process is equal to Q: = 84 kJ

The internal energy change is = Q+W = 83.992 kJ

As is generally the case for liquids, which are nearly incompressible, the internal energy change and the enthalpy change are almost identical.