1.
The SI unit of entropy is ________.
Correct Answer
C. J/K
Explanation
The SI unit of entropy is J/K. Entropy is a measure of the disorder or randomness in a system, and it is defined as the amount of energy that is unavailable for useful work. The unit J/K represents the change in energy per unit temperature, indicating that entropy is dependent on both energy and temperature. This unit allows for the comparison of entropy values across different systems and provides a standardized measurement for this thermodynamic property.
2.
What is entropy?
Correct Answer
A. Entropy is a measure of the disorder of a system.
Explanation
Entropy is a measure of the disorder of a system. In thermodynamics, it quantifies the randomness or chaos within a system. When the entropy of a system increases, it means that the system becomes more disordered. Conversely, when the entropy decreases, the system becomes more ordered. This concept is closely related to the second law of thermodynamics, which states that the entropy of an isolated system always tends to increase over time. Therefore, the correct answer is that entropy is a measure of the disorder of a system.
3.
Gibbs paradox in statistical mechanics is related to
Correct Answer
C. Additive property of the entropy
Explanation
The Gibbs paradox in statistical mechanics is related to the additive property of the entropy. The paradox arises when considering the entropy of an ideal gas composed of identical particles. According to classical statistical mechanics, the entropy of the system should be additive, meaning that the total entropy of the gas should be equal to the sum of the entropies of each individual particle. However, when considering the indistinguishability of particles, it is found that the total entropy is actually greater than this sum. This paradox highlights the need for quantum statistical mechanics to properly account for the behavior of identical particles.
4.
If a liquid crystallizes into a solid, entropy will
Correct Answer
B. Decrease
Explanation
When a liquid crystallizes into a solid, the molecules arrange themselves in a more ordered and structured manner. This increase in orderliness leads to a decrease in the system's entropy. Entropy is a measure of the randomness or disorder in a system, so as the liquid transitions into a solid, the molecules become more organized, resulting in a decrease in entropy.
5.
If 10 g of ice at 0°C is converted to water at the same temperature, the change in entropy will be (latent heat 80 cal/g)
Correct Answer
A. 2.93 cal/K
Explanation
When ice is converted to water at the same temperature, the change in entropy can be calculated using the formula ΔS = Q/T, where ΔS is the change in entropy, Q is the heat transferred, and T is the temperature. In this case, the heat transferred is the latent heat, which is given as 80 cal/g. Since we have 10 g of ice, the heat transferred is 80 cal/g * 10 g = 800 cal. The temperature remains constant at 0°C, which is equivalent to 273 K. Plugging these values into the formula, we get ΔS = 800 cal / 273 K = 2.93 cal/K. Therefore, the correct answer is 2.93 cal/K.
6.
If 30 J of energy is added to water in the form of heat at 27 °C, what is the change in entropy of water?
Correct Answer
D. 0.100 J/K
Explanation
When energy is added to a substance in the form of heat, the change in entropy can be calculated using the equation ΔS = Q/T, where ΔS is the change in entropy, Q is the heat energy, and T is the temperature. In this case, the heat energy added to the water is 30 J and the temperature is 27 °C, which is equivalent to 300 K. Plugging these values into the equation, we get ΔS = 30 J / 300 K = 0.1 J/K. Therefore, the change in entropy of the water is 0.1 J/K.
7.
In steam tables, the entropy is shown a zero for
Correct Answer
D. Saturated liquid at 0° C
Explanation
In steam tables, the entropy is shown as zero for saturated liquid at 0°C because at this state, the substance is in a perfectly ordered and condensed form. The entropy of a substance is a measure of its disorder or randomness. Since the saturated liquid at 0°C is in its most condensed state, it has the least amount of disorder and hence its entropy is zero.
8.
If a liquid crystallizes into a solid, entropy will be:
Correct Answer
B. Decreased
Explanation
When a liquid crystallizes into a solid, the particles in the liquid arrange themselves into a more ordered and structured pattern. This increase in order reduces the number of possible arrangements of the particles, resulting in a decrease in entropy. Therefore, the correct answer is decreased.
9.
The Gibbs function (G) in thermodynamics is defined as G = H - TS (where H = enthalpy, T = temperature, S = entropy). In an isothermal, isobaric, reversible process, G
Correct Answer
B. Remains constant, but is not zero
Explanation
In an isothermal, isobaric, reversible process, the Gibbs function (G) remains constant because the enthalpy (H) and entropy (S) also remain constant. However, it is not necessarily zero because the values of H and S can be non-zero. The equation G = H - TS indicates that G can have a non-zero value depending on the values of H, T, and S. Therefore, in this process, G remains constant but is not zero.
10.
Which of the following has the lowest entropy?
Correct Answer
A. Oxygen gas at 0K
Explanation
At absolute zero temperature (0K), the particles in a substance have minimal energy and are in their lowest possible energy state. This means that there is only one possible microstate for the particles, resulting in the lowest possible number of arrangements. As entropy is a measure of the number of possible arrangements or microstates, oxygen gas at 0K has the lowest entropy among the given options.