Question

Q1, The total entropy change of a system and its surrounding is (a) in a(n) (b) process.

1. (a) larger than zero; (b) reversible
2. (a) smaller than zero; (b) reversible
3. (a) equal to zero; (b) reversible
4. (a) equal to zero; (b) irreversible
5. (a) smaller than zero; (b) irreversible

Q2, Standard enthalpy change (ΔH°) of a process involving gases is the enthalpy change of process at

1. 1 atm and 298K.
2. 1 atm and 273K.
3. 273K.
4. 1 atm.
5. 298K.

Q3, The following values are noticed on the phase diagram of CO2: at its triple point:
T3 =216.8 K and P3 =5.11 atm; at its critical point: Tc =304.2 K and Pc =72.9 atm.

Which of the statements below about CO2 is correct?

1. CO2 can exist as liquid at atmospheric pressure if it is brought to a temperature low enough.
2. CO2 cannot exist in liquid phase at atmospheric pressure.

3. CO2 cannot exist as solid if its temperature is higher than its triple point temperature T3.
4. CO2 is said to be in supercritical condition if it is brought to a temperature higher than 304.2 K at atmospheric pressure
5. CO2 cannot exist as vapour if its temperature is brought to lower than its triple point temperature 216.8K.

Q4, For a pure substance:

1. its Gibbs energy always increases with the pressure at constant temperature.
2. its Gibbs energy always increases with the temperature at constant pressure.
3. its Gibbs energy always increases when the substance changes from solid to liquid or from liquid to vapour.
4. its Gibbs energy always decreases when the substance changes from vapour to liquid or from liquid to solid.
5. its Gibbs energy remains unchanged in a reversible phase change process.

Answer 1