Which of the following is spontaneous reaction?
Correct answer: A. Zn + Cu²+ → Zn²+ + Cu
- A. Zn + Cu²+ → Zn²+ + Cu
- B. Fe + H2O → Fe2+ + OH-
- C. 2H2 + O2 → 2H2O
- D. Ag+ + Cl- → AgCl
Explanation
The correct answer is the reaction Zn + Cu²+ → Zn²+ + Cu. This reaction is spontaneous because it has a positive standard cell potential (E°). The reduction potential of Cu²+ (+0.34V) is greater than that of Zn²+ (-0.76V), indicating that Cu²+ is a stronger oxidizing agent than Zn²+. Therefore, Cu²+ can oxidize Zn, making the reaction spontaneous.The other options are incorrect because they do not meet the criteria for spontaneity under standard conditions. Option B involves Fe and water, which do not react spontaneously. Option C (2H2 + O2 → 2H2O) is not spontaneous without external energy input, and Option D (Ag+ + Cl- → AgCl) does not lead to a positive cell potential under standard conditions.
This question appeared on the ETEA MDCAT 2016 paper, which you can sit online with every answer explained.
Report an error
The more specific you are, the faster it gets fixed. A source beats an opinion.
Prefer email? [email protected]
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.
Practise Electrochemistry
696 free Electrochemistry MCQs from Chemistry, each with the correct answer and an explanation. Unlimited attempts, no account needed.
Discussion
Stuck on an option, or know a faster way to get there? Ask or explain it here.
No comments yet. Be the first to explain this one.
Exams that ask Chemistry questions like this
Chemistry is on 14 papers prepared for on TestUstad, and all of them draw the same bank, so this question is worth knowing for every one of them.
More Redox Reactions questions
If one Faraday was to be 30,230 coulombs instead of 96,500 coulombs then charge on an electron is:
Choose the true statement regarding the reaction given below2Na(g) + Cl2(g)--> 2NaCl(s)
The cathode in lead storage battery is made of:
Choose the incorrect statement about corrosion:
Which polyatomic anion is unstable in solution ?
Which of the following have reducing effect: