Question 1

For a chemical reaction to be spontaneous at all temperatures, which of the following conditions must be met?

Accepted Answer

For a reaction to be spontaneous at all temperatures, $\Delta$G$\degree$ must be negative. This occurs when $\Delta$S$\degree$ > 0 and $\Delta$H$\degree$ < 0, as $\Delta$G$\degree$ = $\Delta$H$\degree$ - T$\Delta$S$\degree$.

Question 2

You are given pure samples of pentane, $ \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{3}(l) $, and 1,3-pentadiene, $ \mathrm{CH}_{2}=\mathrm{CHCH}=\mathrm{CHCH}_{3}(l) $ What prediction would you make concerning their standard molar entropies at 298 K?

Accepted Answer

The answer of You are given pure samples of pentane,...

Question 3

Calculate $\Delta$S$\degree$ for the reaction

Accepted Answer

The answer of Calculate $\Delta$S$\degree$ for the reaction  
...

Question 4

In which one of the following pairs will the first system have a higher entropy than the second? Assume P and T are the same for each pair, unless stated otherwise.

Accepted Answer

The answer of In which one of the following pairs...

Question 5

Which relationship or statement best describes $\Delta$S$\degree$ for the following reaction?

Accepted Answer

The answer of Which relationship or statement best describes $\Delta$S$\degree$...

Question 6

Calculate$\Delta$S $\degree$for the reaction

Accepted Answer

Using the formula for Gibbs free energy change:
ΔG = ΔH - TΔS

We have:
ΔG = 0 (because reaction is at equilibrium)
ΔH = F1F1F1S1 - F1F1F1S1F1F1F10
ΔS = F1F1F10S1 - F1F1F1S1

Rearranging the equation, we get:
ΔS = (F1F1F1S1 - F1F1F1S1F1F1F10)/T

Substituting the given values,
0 = F1F1F1S1 - F1F1F1S1F1F1F10 - T (F1F1F10S1 - F1F1F1S1)

Simplifying the equation, we get:
TΔS = F1F1F1S1 - F1F1F1S1F1F1F10 - F1F1F1S1 + F1F1F10S1
TΔS = F1F1F10S1 - F1F1F1S1F1F1F10

Substituting the given values in the above equation, we get:
TΔS = 198.02 J/K

Therefore, the answer is B.

Question 7

Which one of the following changes of state increases the entropy of the system?

Accepted Answer

Sublimation is the process in which a solid directly turns into a gas without going through the liquid state. This increases the entropy of the system since the particles have more freedom to move in the gaseous state than in the solid state, leading to a higher level of disorder.

Question 8

A sample of water is heated at a constant pressure of one atmosphere. Initially, the sample is ice at 260 K, and at the end the sample consists of steam at 400 K. In which of the following 5 K temperature intervals would there be the greatest increase in the entropy of the sample?

Accepted Answer

The answer of A sample of water is heated at...

Question 9

Elemental boron can be formed by reaction of boron trichloride with hydrogen. If $\Delta$S$\degree$ = 80.3 J/K for the reaction above, what is S $\degree$ for BCl₃(g)?

Accepted Answer

The answer of Elemental boron can be formed by reaction...

Question 10

For a chemical reaction to be spontaneous only at high temperatures, which of the following conditions must be met?

Accepted Answer

The reaction is spontaneous only at high temperatures, which means that $\Delta$G$\degree$ > 0 at low temperatures and $\Delta$G$\degree$ < 0 at high temperatures. This can only be the case if $\Delta$H$\degree$ > 0 and $\Delta$S$\degree$ > 0.

Question 11

You are given pure samples of ammonia, NH₃(g), and nitrogen trifluoride, NF₃(g). What prediction would you make concerning their standard molar entropies at 298 K?

Accepted Answer

Nitrogen trifluoride (NF3) is a larger and more complex molecule than ammonia (NH3), which generally leads to a higher standard molar entropy due to more possible molecular motions and configurations.

Question 12

For a chemical reaction to be non-spontaneous at any temperature, which of the following conditions must be met?

Accepted Answer

For a reaction to be non-spontaneous, the Gibbs free energy change (∆G) must be positive. This means that ∆H (enthalpy change) must be positive and ∆S (entropy change) must be negative. Thus, choice D is the only option where both conditions (∆H > 0 and ∆S < 0) are met.

Question 13

Which relationship or statement best describes $\Delta$S$\degree$for the following reaction?

Accepted Answer

The answer of Which relationship or statement best describes $\Delta$S$\degree$for...

Question 14

For a chemical reaction to be spontaneous only at low temperatures, which of the following conditions must be met?

Accepted Answer

For a reaction to be spontaneous only at low temperatures, $\Delta$H$\degree$ should be negative and $\Delta$S$\degree$ should be negative. This ensures that the reaction is exothermic and the entropy decreases, making it spontaneous at low temperatures.

Question 15

In which one of these pairs will the entropy of the first substance be greater than that of the second? Assume P and T are the same for each pair, unless stated otherwise.

Accepted Answer

The answer of In which one of these pairs will...

Question 16

Which one of the following phase changes decreases the entropy of the system?

Accepted Answer

During condensation, a gas phase changes to a liquid phase which results in a decrease in the entropy of the system. This is because the molecules in the liquid phase are closer together and less randomly arranged than in the gas phase, which leads to a decrease in the number of possible microstates and therefore a decrease in the entropy.

Question 17

Calculate $\Delta$S$\degree$ for the reaction

Accepted Answer

The answer of Calculate $\Delta$S$\degree$ for the reaction  
...

Question 18

You are given pure samples of ethane, C₂H₆(g), and toluene, C₇H₈(l). What prediction would you make concerning their standard molar entropies at 298 K?

Accepted Answer

The answer of You are given pure samples of ethane,...

Question 19

Which of the following pairs has the member with the greater molar entropy listed first? All systems are at 25 $\degree$C.

Accepted Answer

The answer of Which of the following pairs has the...

Question 20

Calculate$\Delta$S$\degree$ for the combustion of propane.

Accepted Answer

The given equation for the combustion of propane is:
C3H8(g) + 5O2(g) → 3CO2(g) + 4H2O(l)
Let's first calculate the standard enthalpy of formation (∆Hf) for propane:
∆Hf(C3H8) = -104.67 kJ/mol
Next, we can calculate the standard enthalpy of combustion (∆Hc) for propane using the enthalpies of formation of the reactants and products:
∆Hc = 3∆Hf(CO2) + 4∆Hf(H2O) - ∆Hf(C3H8) - 5∆Hf(O2)
Plugging in the values, we get:
∆Hc = -2043.45 kJ/mol
Now, we can use the following equation to calculate the standard entropy of combustion (∆Sc) for propane:
∆Sc = ∆Hc/T
Plugging in the values, we get:
∆Sc = -100.9 J/K
Therefore, the correct answer is D) -100.9 J/K.

Quiz 20: Thermodynamics: Entropy, Free Energy, and the Direction of Chemical Reactions

For a chemical reaction to be spontaneous at all temperatures, which of the following conditions must be met?

You are given pure samples of pentane, $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{3}(l)$ , and 1,3-pentadiene, $\mathrm{CH}_{2}=\mathrm{CHCH}=\mathrm{CHCH}_{3}(l)$ What prediction would you make concerning their standard molar entropies at 298 K?

Calculate $\Delta$ S $\degree$ for the reaction $Calculate \Delta S \degree for the reaction A) -118.2 J/K B) -104.8 J/K C) 104.8 J/K D) 118.2 J/K E) 1270.0 J/K$ $Calculate \Delta S \degree for the reaction A) -118.2 J/K B) -104.8 J/K C) 104.8 J/K D) 118.2 J/K E) 1270.0 J/K$

In which one of the following pairs will the first system have a higher entropy than the second? Assume P and T are the same for each pair, unless stated otherwise.

Calculate $\Delta$ S $\degree$ for the reaction $Calculate \Delta S \degree for the reaction A) -254.96 J/K B) -198.02 J/K C) 198.02 J/K D) 254.96 J/K E) 471.86 J/K$ $Calculate \Delta S \degree for the reaction A) -254.96 J/K B) -198.02 J/K C) 198.02 J/K D) 254.96 J/K E) 471.86 J/K$

Which one of the following changes of state increases the entropy of the system?

A sample of water is heated at a constant pressure of one atmosphere. Initially, the sample is ice at 260 K, and at the end the sample consists of steam at 400 K. In which of the following 5 K temperature intervals would there be the greatest increase in the entropy of the sample?

For a chemical reaction to be spontaneous only at high temperatures, which of the following conditions must be met?

You are given pure samples of ammonia, NH₃(g) , and nitrogen trifluoride, NF₃(g) . What prediction would you make concerning their standard molar entropies at 298 K?

For a chemical reaction to be non-spontaneous at any temperature, which of the following conditions must be met?

For a chemical reaction to be spontaneous only at low temperatures, which of the following conditions must be met?

In which one of these pairs will the entropy of the first substance be greater than that of the second? Assume P and T are the same for each pair, unless stated otherwise.

Which one of the following phase changes decreases the entropy of the system?

Calculate $\Delta$ S $\degree$ for the reaction $Calculate \Delta S \degree for the reaction A) -548.1 J/K B) -147.7 J/K C) 147.7 J/K D) 310.1 J/K E) 548.1 J/K$ $Calculate \Delta S \degree for the reaction A) -548.1 J/K B) -147.7 J/K C) 147.7 J/K D) 310.1 J/K E) 548.1 J/K$

You are given pure samples of ethane, C₂H₆(g) , and toluene, C₇H₈(l) . What prediction would you make concerning their standard molar entropies at 298 K?

Which of the following pairs has the member with the greater molar entropy listed first? All systems are at 25 $\degree$ C.

Quiz 20: Thermodynamics: Entropy, Free Energy, and the Direction of Chemical Reactions

For a chemical reaction to be spontaneous at all temperatures, which of the following conditions must be met?

Calculate Δ\DeltaΔ S °\degree° for the reaction

In which one of the following pairs will the first system have a higher entropy than the second? Assume P and T are the same for each pair, unless stated otherwise.

Which relationship or statement best describes Δ\DeltaΔ S °\degree° for the following reaction?

Calculate Δ\DeltaΔ S °\degree° for the reaction

Which one of the following changes of state increases the entropy of the system?

A sample of water is heated at a constant pressure of one atmosphere. Initially, the sample is ice at 260 K, and at the end the sample consists of steam at 400 K. In which of the following 5 K temperature intervals would there be the greatest increase in the entropy of the sample?

Elemental boron can be formed by reaction of boron trichloride with hydrogen. If Δ\DeltaΔ S °\degree° = 80.3 J/K for the reaction above, what is S °\degree° for BCl3(g) ?

For a chemical reaction to be spontaneous only at high temperatures, which of the following conditions must be met?

You are given pure samples of ammonia, NH3(g) , and nitrogen trifluoride, NF3(g) . What prediction would you make concerning their standard molar entropies at 298 K?

For a chemical reaction to be non-spontaneous at any temperature, which of the following conditions must be met?

Which relationship or statement best describes Δ\DeltaΔ S °\degree° for the following reaction?

For a chemical reaction to be spontaneous only at low temperatures, which of the following conditions must be met?

In which one of these pairs will the entropy of the first substance be greater than that of the second? Assume P and T are the same for each pair, unless stated otherwise.

Which one of the following phase changes decreases the entropy of the system?

Calculate Δ\DeltaΔ S °\degree° for the reaction

You are given pure samples of ethane, C2H6(g) , and toluene, C7H8(l) . What prediction would you make concerning their standard molar entropies at 298 K?

Which of the following pairs has the member with the greater molar entropy listed first? All systems are at 25 °\degree° C.

Calculate Δ\DeltaΔ S °\degree° for the combustion of propane.

Calculate $\Delta$ S $\degree$ for the reaction $Calculate \Delta S \degree for the reaction A) -118.2 J/K B) -104.8 J/K C) 104.8 J/K D) 118.2 J/K E) 1270.0 J/K$ $Calculate \Delta S \degree for the reaction A) -118.2 J/K B) -104.8 J/K C) 104.8 J/K D) 118.2 J/K E) 1270.0 J/K$

Calculate $\Delta$ S $\degree$ for the reaction $Calculate \Delta S \degree for the reaction A) -254.96 J/K B) -198.02 J/K C) 198.02 J/K D) 254.96 J/K E) 471.86 J/K$ $Calculate \Delta S \degree for the reaction A) -254.96 J/K B) -198.02 J/K C) 198.02 J/K D) 254.96 J/K E) 471.86 J/K$

You are given pure samples of ammonia, NH₃(g) , and nitrogen trifluoride, NF₃(g) . What prediction would you make concerning their standard molar entropies at 298 K?

Calculate $\Delta$ S $\degree$ for the reaction $Calculate \Delta S \degree for the reaction A) -548.1 J/K B) -147.7 J/K C) 147.7 J/K D) 310.1 J/K E) 548.1 J/K$ $Calculate \Delta S \degree for the reaction A) -548.1 J/K B) -147.7 J/K C) 147.7 J/K D) 310.1 J/K E) 548.1 J/K$

You are given pure samples of ethane, C₂H₆(g) , and toluene, C₇H₈(l) . What prediction would you make concerning their standard molar entropies at 298 K?

Which of the following pairs has the member with the greater molar entropy listed first? All systems are at 25 $\degree$ C.