The normal boiling point of Br 2 (l) is 58.8 °C, and its molar enthalpy of vaporization is ΔHvap = 29.6 kJ/mol. (a) When Br 2 (l) boils at its normal boiling point, does its entropy increase or decrease?

Hey everyone worse hold that acetone has a normal boiling point of 56°C and a molar entropy of vaporization of 29. kg Permal predict whether the entropy of acetone will increase or decrease when it boils at its normal boiling point first. Let's go ahead and write out our reaction. So at our boiling point we have acetone and this is going to be in its liquid state and then it will transform into its gaseous state. So as we can see right here, we're converting from a liquid to a gas. And as we've learned when we go from a solid to a liquid to a gas, this means that we increase our entropy and if we were to go from a gas to liquid to solid, this means that we would decrease entropy. And essentially the reason why is because we have more gas molecules, which means we have more random motion which leads to a higher entropy. So our answer here is going to be that the entropy of acetone will increase when it boils at its normal boiling point. Now, I hope that made sense. And let us know if you have any questions

Ch.19 - Chemical Thermodynamics

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Brown 15th Edition

Ch.19 - Chemical Thermodynamics

Problem 23a

Chapter 19, Problem 23a

The normal boiling point of Br₂(l) is 58.8 °C, and its molar enthalpy of vaporization is ΔHvap = 29.6 kJ/mol. (a) When Br₂(l) boils at its normal boiling point, does its entropy increase or decrease?

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Identify the phase change occurring: Boiling is a phase change from liquid to gas.

Understand the nature of the phases: In the liquid phase, molecules are more ordered compared to the gas phase where molecules are more dispersed and have higher randomness.

Relate entropy to randomness: Entropy, a measure of disorder or randomness in a system, increases when a substance transitions from a more ordered state (liquid) to a less ordered state (gas).

Apply this understanding to the boiling of Br₂(l): As Br₂(l) boils and changes from liquid to gas, the entropy of the system increases due to the increased disorder and freedom of movement of the gas molecules compared to the liquid.

Conclude the effect on entropy: Therefore, when Br₂(l) boils at its normal boiling point, its entropy increases.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Entropy

Entropy is a measure of the disorder or randomness in a system. In thermodynamics, it is often associated with the number of ways a system can be arranged. When a substance transitions from a liquid to a gas, such as bromine (Br2) boiling, the molecules move from a more ordered state to a less ordered state, leading to an increase in entropy.

Phase Change

A phase change refers to the transition of a substance from one state of matter to another, such as from liquid to gas during boiling. This process involves energy changes, specifically the enthalpy of vaporization, which is the energy required to convert a unit amount of a liquid into vapor at its boiling point. Understanding phase changes is crucial for analyzing changes in entropy.

Enthalpy of Vaporization

The enthalpy of vaporization (ΔHvap) is the amount of energy required to convert one mole of a liquid into vapor at constant temperature and pressure. For bromine, this value is 29.6 kJ/mol. This energy input not only facilitates the phase change but also contributes to the increase in entropy, as the molecules in the gas phase have greater freedom of movement compared to those in the liquid phase.

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Textbook Question

A system goes from state 1 to state 2 and back to state 1 following a reversible path in both directions. Which of the following statements about this process is or are true?

c. The value of w on going from state 1 to state 2 is equal in magnitude and opposite in sign to the value of w on going from state 2 back to state 1.

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Textbook Question

Indicate whether each statement is true or false. (a) ΔS is a state function. (b) If a system undergoes a reversible change, the entropy of the universe increases. (c) If a system undergoes a reversible process, the change in entropy of the system is exactly matched by an equal and opposite change in the entropy of the surroundings. (d) If a system undergoes a reversible process, the entropy change of the system must be zero.

Textbook Question

The normal boiling point of Br₂(𝑙) is 58.8 °C, and its molar enthalpy of vaporization is Δ𝐻_vap=29.6kJ/mol. (b) Calculate the value of Δ𝑆 when 1.00 mol of Br2(𝑙) is vaporized at 58.8 °C.

Textbook Question

The element gallium (Ga) freezes at 29.8 °C, and its molar enthalpy of fusion is ΔH_fus = 5.59 kJ/mol. (a) When molten gallium solidifies to Ga(s) at its normal melting point, is ΔS positive or negative?

Textbook Question

The element gallium (Ga) freezes at 29.8 °C, and its molar enthalpy of fusion is ΔH_fus = 5.59 kJ/mol. (b) Calculate the value of ΔS when 60.0 g of Ga(l) solidifies at 29.8 °C.

The normal boiling point of Br2(l) is 58.8 °C, and its molar enthalpy of vaporization is ΔHvap = 29.6 kJ/mol. (a) When Br2(l) boils at its normal boiling point, does its entropy increase or decrease?

Verified video answer for a similar problem:

Key Concepts

Entropy

Phase Change

Enthalpy of Vaporization

The normal boiling point of Br₂(l) is 58.8 °C, and its molar enthalpy of vaporization is ΔHvap = 29.6 kJ/mol. (a) When Br₂(l) boils at its normal boiling point, does its entropy increase or decrease?