Q. At constant temperature and pressure, if ΔH is positive and ΔS is negative, what can be said about ΔG?
-
A.
ΔG is positive
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B.
ΔG is negative
-
C.
ΔG is zero
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D.
ΔG can be either positive or negative
Solution
If ΔH is positive and ΔS is negative, ΔG will be positive.
Correct Answer: A — ΔG is positive
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Q. At constant temperature and pressure, if ΔH is positive and ΔS is negative, what is the sign of ΔG?
-
A.
Always negative
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B.
Always positive
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C.
Depends on temperature
-
D.
Zero
Solution
If ΔH is positive and ΔS is negative, ΔG will always be positive.
Correct Answer: B — Always positive
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Q. At what temperature does a reaction become spontaneous if ΔH = 50 kJ and ΔS = 0.1 kJ/K?
-
A.
500 K
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B.
250 K
-
C.
1000 K
-
D.
200 K
Solution
Set ΔG = 0: 0 = ΔH - TΔS; T = ΔH/ΔS = 50 kJ / 0.1 kJ/K = 500 K.
Correct Answer: A — 500 K
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Q. At what temperature does the Gibbs Free Energy change from negative to positive?
-
A.
At absolute zero
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B.
At the melting point
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C.
At the boiling point
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D.
At the transition temperature
Solution
The Gibbs Free Energy changes from negative to positive at the transition temperature, where the system shifts from one phase to another.
Correct Answer: D — At the transition temperature
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Q. For a process with ΔH = 200 kJ and ΔS = 0.5 kJ/K, what is ΔG at 400 K?
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A.
200 kJ
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B.
180 kJ
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C.
220 kJ
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D.
160 kJ
Solution
ΔG = ΔH - TΔS = 200 kJ - 400 K * 0.5 kJ/K = 200 kJ - 200 kJ = 0 kJ.
Correct Answer: B — 180 kJ
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Q. For a reaction at constant temperature and pressure, which of the following is true?
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A.
ΔG = ΔH + TΔS
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B.
ΔG = ΔH - TΔS
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C.
ΔG = TΔS - ΔH
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D.
ΔG = ΔS - ΔH
Solution
The correct relationship at constant temperature and pressure is ΔG = ΔH - TΔS.
Correct Answer: B — ΔG = ΔH - TΔS
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Q. For a reaction at standard conditions, if ΔG° is negative, what can be said about the equilibrium constant (K)?
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A.
K < 1
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B.
K = 1
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C.
K > 1
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D.
K is undefined
Solution
If ΔG° is negative, the equilibrium constant K is greater than 1.
Correct Answer: C — K > 1
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Q. For a reaction at standard conditions, if ΔG° is positive, what can be said about the reaction?
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A.
The reaction is spontaneous in the forward direction.
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B.
The reaction is spontaneous in the reverse direction.
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C.
The reaction is at equilibrium.
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D.
The reaction is impossible.
Solution
A positive ΔG° indicates that the reaction is non-spontaneous in the forward direction, thus spontaneous in the reverse.
Correct Answer: B — The reaction is spontaneous in the reverse direction.
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Q. For a reaction at standard conditions, if ΔG° is positive, what does it imply?
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A.
The reaction is spontaneous in the forward direction.
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B.
The reaction is at equilibrium.
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C.
The reaction is non-spontaneous in the forward direction.
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D.
The reaction will proceed rapidly.
Solution
A positive ΔG° indicates that the reaction is non-spontaneous in the forward direction under standard conditions.
Correct Answer: C — The reaction is non-spontaneous in the forward direction.
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Q. For a reaction at standard conditions, if ΔG° is positive, what does it indicate?
-
A.
The reaction is spontaneous in the forward direction.
-
B.
The reaction is non-spontaneous in the forward direction.
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C.
The reaction is at equilibrium.
-
D.
The reaction is spontaneous in the reverse direction.
Solution
A positive ΔG° indicates that the reaction is non-spontaneous in the forward direction.
Correct Answer: B — The reaction is non-spontaneous in the forward direction.
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Q. For a reaction with ΔH = 100 kJ and ΔS = 200 J/K, at what temperature will the reaction become spontaneous?
-
A.
500 K
-
B.
250 K
-
C.
200 K
-
D.
100 K
Solution
To find the temperature at which the reaction becomes spontaneous, set ΔG = 0: 0 = ΔH - TΔS. Thus, T = ΔH/ΔS = (100,000 J)/(200 J/K) = 500 K.
Correct Answer: A — 500 K
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Q. For a reaction with ΔH = 100 kJ/mol and ΔS = 200 J/mol·K, at what temperature will the reaction become spontaneous?
-
A.
500 K
-
B.
250 K
-
C.
200 K
-
D.
100 K
Solution
To find the temperature at which the reaction becomes spontaneous, set ΔG = 0: 0 = ΔH - TΔS, thus T = ΔH/ΔS = 100,000 J / 200 J/K = 500 K.
Correct Answer: A — 500 K
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Q. For a reaction with ΔH = 50 kJ/mol and ΔS = 100 J/mol·K, at what temperature will the reaction become spontaneous?
-
A.
500 K
-
B.
250 K
-
C.
1000 K
-
D.
200 K
Solution
To find the temperature at which the reaction becomes spontaneous, set ΔG = 0: 0 = ΔH - TΔS, thus T = ΔH/ΔS = (50,000 J/mol) / (100 J/mol·K) = 500 K.
Correct Answer: A — 500 K
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Q. If a reaction has a ΔG of +5 kJ/mol, what can be inferred?
-
A.
The reaction is spontaneous
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B.
The reaction is non-spontaneous
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C.
The reaction is at equilibrium
-
D.
The reaction is exothermic
Solution
A ΔG of +5 kJ/mol indicates that the reaction is non-spontaneous.
Correct Answer: B — The reaction is non-spontaneous
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Q. If a reaction has ΔH = 100 kJ and ΔS = -200 J/K, what is ΔG at 298 K?
-
A.
0 kJ
-
B.
100 kJ
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C.
200 kJ
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D.
300 kJ
Solution
ΔG = ΔH - TΔS = 100 kJ - 298 K * (-0.2 kJ/K) = 100 kJ + 59.6 kJ = 159.6 kJ.
Correct Answer: D — 300 kJ
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Q. If the entropy of a system increases, what is the effect on Gibbs Free Energy at constant temperature?
-
A.
ΔG increases
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B.
ΔG decreases
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C.
ΔG remains constant
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D.
ΔG becomes zero
Solution
If entropy increases, ΔG decreases, making the reaction more favorable.
Correct Answer: B — ΔG decreases
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Q. If ΔG is negative for a reaction, what can be inferred about the reaction?
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A.
The reaction is at equilibrium.
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B.
The reaction is spontaneous.
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C.
The reaction is non-spontaneous.
-
D.
The reaction requires energy input.
Solution
A negative ΔG indicates that the reaction is spontaneous.
Correct Answer: B — The reaction is spontaneous.
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Q. If ΔG is negative for a reaction, what can be inferred?
-
A.
The reaction is non-spontaneous.
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B.
The reaction is at equilibrium.
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C.
The reaction is spontaneous.
-
D.
The reaction requires energy input.
Solution
A negative ΔG indicates that the reaction is spontaneous under the given conditions.
Correct Answer: C — The reaction is spontaneous.
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Q. If ΔG is negative, what does it indicate about the reaction?
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A.
Reaction is at equilibrium
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B.
Reaction is spontaneous
-
C.
Reaction is non-spontaneous
-
D.
Reaction requires energy input
Solution
A negative ΔG indicates that the reaction is spontaneous.
Correct Answer: B — Reaction is spontaneous
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Q. If ΔG is positive, what can be inferred about the reaction?
-
A.
The reaction is spontaneous.
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B.
The reaction is at equilibrium.
-
C.
The reaction is non-spontaneous.
-
D.
The reaction will proceed in reverse.
Solution
If ΔG is positive, the reaction is non-spontaneous under the given conditions.
Correct Answer: C — The reaction is non-spontaneous.
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Q. If ΔH = 100 kJ and ΔS = 0.2 kJ/K, what is ΔG at 298 K?
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A.
100 kJ
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B.
96 kJ
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C.
104 kJ
-
D.
90 kJ
Solution
ΔG = ΔH - TΔS = 100 kJ - 298 K * 0.2 kJ/K = 100 kJ - 59.6 kJ = 40.4 kJ.
Correct Answer: B — 96 kJ
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Q. If ΔH is negative and ΔS is positive, what can be said about ΔG?
-
A.
ΔG is always positive.
-
B.
ΔG is always negative.
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C.
ΔG can be positive or negative depending on temperature.
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D.
ΔG is zero.
Solution
If ΔH is negative and ΔS is positive, ΔG will always be negative, indicating that the reaction is spontaneous at all temperatures.
Correct Answer: B — ΔG is always negative.
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Q. In a reaction where ΔH is negative and ΔS is positive, what can be said about ΔG?
-
A.
ΔG is always negative.
-
B.
ΔG is always positive.
-
C.
ΔG is zero.
-
D.
ΔG depends on temperature.
Solution
If ΔH is negative and ΔS is positive, ΔG will always be negative at all temperatures.
Correct Answer: A — ΔG is always negative.
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Q. In a reaction where ΔH is positive and ΔS is negative, what is the sign of ΔG at high temperatures?
-
A.
Positive
-
B.
Negative
-
C.
Zero
-
D.
Cannot be determined
Solution
At high temperatures, ΔG will be positive because the positive ΔH and negative ΔS will dominate the equation ΔG = ΔH - TΔS.
Correct Answer: A — Positive
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Q. In which of the following scenarios is ΔG equal to ΔH?
-
A.
At high temperatures with ΔS = 0.
-
B.
At low temperatures with ΔS = 0.
-
C.
At constant pressure and temperature.
-
D.
In a phase transition.
Solution
During a phase transition, such as melting or boiling, ΔG equals ΔH because the system is at equilibrium.
Correct Answer: D — In a phase transition.
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Q. In which scenario would the Gibbs Free Energy of a system be at its minimum?
-
A.
At equilibrium
-
B.
At the start of a reaction
-
C.
At maximum temperature
-
D.
At maximum pressure
Solution
The Gibbs Free Energy of a system is at its minimum at equilibrium, indicating stability.
Correct Answer: A — At equilibrium
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Q. In which scenario would ΔG = 0?
-
A.
At the start of a reaction.
-
B.
At equilibrium.
-
C.
When the reaction is spontaneous.
-
D.
When the reaction is non-spontaneous.
Solution
ΔG = 0 occurs at equilibrium, where the forward and reverse reactions occur at the same rate.
Correct Answer: B — At equilibrium.
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Q. In which scenario would ΔG be equal to ΔH?
-
A.
At absolute zero.
-
B.
When ΔS = 0.
-
C.
For a spontaneous reaction.
-
D.
For an endothermic reaction.
Solution
ΔG equals ΔH when the entropy change (ΔS) is zero, indicating no change in disorder.
Correct Answer: B — When ΔS = 0.
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Q. In which scenario would ΔG be zero?
-
A.
At standard conditions
-
B.
At equilibrium
-
C.
In a spontaneous reaction
-
D.
In a non-spontaneous reaction
Solution
ΔG is zero at equilibrium, indicating no net change in the concentrations of reactants and products.
Correct Answer: B — At equilibrium
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Q. What does a large negative value of ΔG indicate about a reaction?
-
A.
The reaction is highly spontaneous.
-
B.
The reaction is non-spontaneous.
-
C.
The reaction is at equilibrium.
-
D.
The reaction requires a catalyst.
Solution
A large negative value of ΔG indicates that the reaction is highly spontaneous and favors the formation of products.
Correct Answer: A — The reaction is highly spontaneous.
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