Multiple Choice
Which of the following statements is true regarding the relationship between spontaneity and reaction rate?
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19. Chemical Thermodynamics
Spontaneous vs Nonspontaneous Reactions
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Which of the following statements is/are true?
a) The rusting of iron by oxygen is a non-spontaneous reaction.
b) The addition of a catalyst to a reaction increases spontaneity.
c) The movement of heat from a cold object to a hot object is a non-spontaneous reaction.
d) The diffusion of perfume molecules from one side of a room to the other is a non-spontaneous reaction.
e) None of the above.
A
C
B
A,C
C
D
D
B,C
Verified step by step guidance1
Step 1: Understand the concept of spontaneity in chemical reactions. A spontaneous reaction is one that occurs naturally under given conditions without external intervention. It is often associated with a negative Gibbs free energy change (ΔG < 0).
Step 2: Evaluate statement (a): The rusting of iron by oxygen is a spontaneous reaction. Rusting is a natural process that occurs when iron reacts with oxygen in the presence of moisture, leading to the formation of iron oxide. This process is thermodynamically favorable and spontaneous.
Step 3: Evaluate statement (b): The addition of a catalyst to a reaction does not affect the spontaneity of the reaction. Catalysts speed up the rate of a reaction by lowering the activation energy but do not change the Gibbs free energy of the reaction, thus not affecting spontaneity.
Step 4: Evaluate statement (c): The movement of heat from a cold object to a hot object is non-spontaneous. According to the second law of thermodynamics, heat naturally flows from hot to cold, making the reverse process non-spontaneous without external work.
Step 5: Evaluate statement (d): The diffusion of perfume molecules from one side of a room to the other is a spontaneous process. Diffusion occurs naturally as molecules move from an area of higher concentration to an area of lower concentration, driven by entropy increase.
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