Multiple Choice
A positive ΔSsystem indicates what about the overall spontaneity of a process?
19. Chemical Thermodynamics
Spontaneous vs Nonspontaneous Reactions
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Which of the following would have a negative ΔS?
A
the sublimation of carbon dioxide
B
the dissolving of solid NaCl in water to make an aqueous solution
C
the decomposition of liquid water into hydrogen gas and oxygen gas
D
the formation of ice from water at −25℃
E
the decomposition of carbon dioxide gas into carbon monoxide gas and oxygen gas
Verified step by step guidance1
Understand that entropy (ΔS) is a measure of disorder or randomness in a system. A negative ΔS indicates a decrease in disorder.
Consider the process of sublimation of carbon dioxide. Sublimation is the transition from a solid to a gas, which increases disorder, thus ΔS would be positive.
Analyze the dissolving of solid NaCl in water. Dissolving increases the number of particles in solution, leading to increased disorder, so ΔS would be positive.
Examine the decomposition of liquid water into hydrogen gas and oxygen gas. This process increases the number of gas molecules, increasing disorder, so ΔS would be positive.
Evaluate the formation of ice from water at −25℃. This process involves the transition from a liquid to a solid, which decreases disorder, resulting in a negative ΔS.
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