Given that the normal boiling point of CCl4 is 77 °C, which of the following statements about the process below is/are correct? You may choose more than one, or none, of the statements.
CCl4(l, 68 °C, 1 atm) ⟶ CCl4(g, 101 °C, 1 atm)
Assume that the temperature of the surroundings is constant and also equal to 101 °C.
Note: The normal boiling point (Tnbp) is the boiling temperature at 1 atm. The phase change is reversible at the normal boiling point but irreversible if P = 1 atm and T ≠ Tnbp.
a. The entropy of the system increases: ΔS > 0.
b. The entropy of the surroundings increases: ΔSsurr > 0.
c. The entropy of the universe increases: ΔSuniv > 0.
d. Work is done by the system on the surroundings.
e. Heat flows from the system into the surroundings.
f. The entropy change for the system is equal to ΔH / Tvap.
g. The entropy change for the system is equal to ΔH / Tsurr.
h. The process is thermodynamically reversible.
would be grateful if you can explain how to solve this question
I think you could make some picks if you just looked up the definitions. For example, If CCl4 changes from a liquid to a gas, you know molecules are more random in a gas than in the liquide; therefore, disorder has increased so dS must be > 0. So you pick a. For c, you KNOW that the universe is increasing disorder. That's c. etc.
To analyze the given process step-by-step and determine which statements are correct, let's go through each option:
a. The entropy of the system increases: ΔS > 0.
Entropy is related to the degree of disorder or randomness in a system. Since the CCl4 is transitioning from a liquid phase to a gaseous phase, which is more disordered, the entropy of the system increases. Therefore, statement a is correct.
b. The entropy of the surroundings increases: ΔSsurr > 0.
When a substance evaporates, heat is absorbed from the surroundings, leading to an increase in entropy. Therefore, statement b is correct.
c. The entropy of the universe increases: ΔSuniv > 0.
The total entropy change of the universe can be calculated by adding the changes in the system and the surroundings. Since both the system and the surroundings experience an increase in entropy, the overall entropy change of the universe is positive. Therefore, statement c is correct.
d. Work is done by the system on the surroundings.
In this process, the CCl4 is evaporating and expanding into the surroundings, which means work is done by the system on the surroundings. Therefore, statement d is correct.
e. Heat flows from the system into the surroundings.
During the process of evaporation, heat is absorbed from the surroundings, causing the temperature of the system to decrease. Therefore, statement e is incorrect. Heat is flowing into the system, not into the surroundings.
f. The entropy change for the system is equal to ΔH / Tvap.
The entropy change for the system during a phase change can be calculated using ΔS = ΔH / T, where ΔH is the enthalpy change and T is the temperature. However, in this case, we are given the temperature at which the vapor is formed, not the heat of vaporization. Therefore, statement f cannot be determined.
g. The entropy change for the system is equal to ΔH / Tsurr.
The entropy change for the system during a phase change can be calculated using ΔS = ΔH / T, where ΔH is the enthalpy change and T is the temperature. However, in this case, Tsurr refers to the temperature of the surroundings, not the system. Therefore, statement g is incorrect.
h. The process is thermodynamically reversible.
The process described is not reversible since it does not occur at the normal boiling point. Therefore, statement h is incorrect.
To summarize, the correct statements are:
a. The entropy of the system increases: ΔS > 0.
b. The entropy of the surroundings increases: ΔSsurr > 0.
c. The entropy of the universe increases: ΔSuniv > 0.
d. Work is done by the system on the surroundings.
To determine which statements about the given process are correct, we can analyze the changes in entropy, work, heat flow, and thermodynamic reversibility.
a. The entropy of the system increases: ΔS > 0.
To determine the entropy change of the system, we need to compare the entropy of the initial state with the entropy of the final state. Since the substance undergoes a phase change from liquid to gas, the entropy of the system increases. Therefore, statement a is correct.
b. The entropy of the surroundings increases: ΔSsurr > 0.
When a substance evaporates, the surrounding molecules need to make room for the gaseous molecules, leading to an increase in entropy of the surroundings. Therefore, statement b is correct.
c. The entropy of the universe increases: ΔSuniv > 0.
The change in entropy of the universe is the sum of the changes in entropy of the system and the surroundings. Since both the system and the surroundings experience an increase in entropy, the entropy of the universe increases. Therefore, statement c is correct.
d. Work is done by the system on the surroundings.
For a phase change process occurring at constant pressure, no work is done. Therefore, statement d is incorrect.
e. Heat flows from the system into the surroundings.
Since the temperature of the surroundings is equal to the final temperature of the system, heat flows from the system into the surroundings during the phase change. Therefore, statement e is correct.
f. The entropy change for the system is equal to ΔH / Tvap.
The equation ΔS = ΔH / Tvap is valid for an isothermal reversible process, which is not the case here since the temperature of the surroundings is higher than the normal boiling point. Therefore, statement f is incorrect.
g. The entropy change for the system is equal to ΔH / Tsurr.
The equation ΔS = ΔH / Tsurr is valid for an isothermal reversible process, which is not the case here since the temperature of the surroundings is higher than the normal boiling point. Therefore, statement g is incorrect.
h. The process is thermodynamically reversible.
Since the process occurs at a temperature higher than the normal boiling point, it is not thermodynamically reversible. Therefore, statement h is incorrect.
In conclusion, the correct statements are a, b, and c.