Q. Which of the following processes has a negative ΔG?
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A.
Melting of ice at 0°C.
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B.
Freezing of water at 0°C.
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C.
Dissolving salt in water.
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D.
Sublimation of dry ice.
Solution
Dissolving salt in water is a spontaneous process at standard conditions, resulting in a negative ΔG.
Correct Answer: C — Dissolving salt in water.
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Q. Which of the following processes has a positive ΔG?
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A.
Combustion of fuels
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B.
Dissolution of salts in water
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C.
Photosynthesis
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D.
Respiration
Solution
Photosynthesis is an endothermic process that requires energy, resulting in a positive ΔG.
Correct Answer: C — Photosynthesis
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Q. Which of the following reactions has a positive ΔG at standard conditions?
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A.
Combustion of glucose
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B.
Formation of water from hydrogen and oxygen
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C.
Dissolution of salt in water
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D.
Decomposition of hydrogen peroxide
Solution
The decomposition of hydrogen peroxide is non-spontaneous under standard conditions, resulting in a positive ΔG.
Correct Answer: D — Decomposition of hydrogen peroxide
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Q. Which of the following reactions is likely to have a negative ΔG?
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A.
Combustion of hydrocarbons.
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B.
Formation of ice from water at 0°C.
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C.
Dissolution of salt in water.
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D.
Decomposition of hydrogen peroxide.
Solution
The combustion of hydrocarbons is highly exothermic and typically has a negative ΔG, indicating spontaneity.
Correct Answer: A — Combustion of hydrocarbons.
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Q. Which of the following reactions is spontaneous at all temperatures?
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A.
ΔH < 0 and ΔS < 0
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B.
ΔH > 0 and ΔS > 0
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C.
ΔH < 0 and ΔS > 0
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D.
ΔH > 0 and ΔS < 0
Solution
A reaction with ΔH < 0 and ΔS > 0 is spontaneous at all temperatures because it results in a negative ΔG.
Correct Answer: C — ΔH < 0 and ΔS > 0
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Q. Which of the following reactions will have a negative ΔG at high temperatures?
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A.
Exothermic reactions with negative ΔS
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B.
Endothermic reactions with positive ΔS
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C.
Exothermic reactions with positive ΔS
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D.
Endothermic reactions with negative ΔS
Solution
Endothermic reactions with positive ΔS can have a negative ΔG at high temperatures due to the TΔS term becoming significant.
Correct Answer: B — Endothermic reactions with positive ΔS
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Q. Which of the following statements is true about Gibbs Free Energy?
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A.
ΔG is always positive for spontaneous processes.
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B.
ΔG = ΔH - TΔS.
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C.
ΔG can never be zero.
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D.
ΔG is independent of temperature.
Solution
The correct equation for Gibbs Free Energy is ΔG = ΔH - TΔS, which relates enthalpy, entropy, and temperature.
Correct Answer: B — ΔG = ΔH - TΔS.
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Q. Which of the following statements is true regarding Gibbs Free Energy?
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A.
ΔG is always positive for spontaneous processes.
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B.
ΔG = ΔH - TΔS.
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C.
ΔG can never be negative.
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D.
ΔG is independent of temperature.
Solution
The correct equation for Gibbs Free Energy is ΔG = ΔH - TΔS, which relates enthalpy, entropy, and temperature.
Correct Answer: B — ΔG = ΔH - TΔS.
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