Which one is a spontaneous chemical reaction?
Correct answer: A. Zn + Cu2+ → Zn2+ + Cu
- A. Zn + Cu2+ → Zn2+ + Cu
- B. Zn2+ + Cu → Cu2+ + Zn
- C. 2 Fe(OH)3 → 2 Fe + 3/2 O2 + 3 H2O
- D. 2NaCl → 2Na + Cl2
Explanation
A spontaneous chemical reaction is one that occurs without continuous external energy input, often characterized by a negative Gibbs free energy change (ΔG). In the reaction Zn + Cu2+ → Zn2+ + Cu, zinc is oxidized while copper ions are reduced, releasing energy in the process, thus making it spontaneous. In contrast, the other reactions are non-spontaneous because they require external energy to proceed. The reaction Zn2+ + Cu → Cu2+ + Zn is the reverse of the spontaneous reaction and requires energy input. The decomposition of Fe(OH)3 and the breakdown of NaCl are both processes that require energy input, hence they are non-spontaneous.
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About Redox Reactions
Redox reactions involve oxidation and reduction occurring together, with electrons transferred between species or oxidation numbers changing. The topic covers assigning oxidation states, identifying oxidizing and reducing agents, balancing redox equations by oxidation number or half-reaction methods, and connecting chemical changes with galvanic and electrolytic cells.
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