Question:
Which of the following reactions is NOT an example of redox reaction?
Which of the following reactions is NOT an example of redox reaction?
Show Hint
In a redox reaction oxidation numbers change; ionisation of HCl in water has no such change.
Updated On: Oct 1, 2026
- \(\text{Cl}_2+2\text{H}_2\text{O}+\text{SO}_2⟶4\text{H}^++\text{SO}_4^{2-}+2\text{Cl}^-\)
- \(\text{Cu}^{2+}+\text{Zn}⟶\text{Cu}+\text{Zn}^{2+}\)
- \(2\text{H}_2+\text{O}_2⟶2\text{H}_2\text{O}\)
- \(\text{HCl}+\text{H}_2\text{O}⟶\text{H}_3\text{O}^++\text{Cl}^-\)
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The Correct Option is D
Solution and Explanation
Step 1: Understanding the Concept
A redox reaction has a change in oxidation number of at least one element. If no oxidation numbers change, the reaction is not redox.
Step 2: Detailed Explanation
(A) Cl\(_2\) goes from 0 to \(-1\), and S in SO\(_2\) goes from \(+4\) to \(+6\): redox.
(B) Zn goes from 0 to \(+2\) and Cu goes from \(+2\) to 0: redox.
(C) H goes from 0 to \(+1\) and O goes from 0 to \(-2\): redox.
(D) \(\text{HCl}+\text{H}_2\text{O}\to\text{H}_3\text{O}^++\text{Cl}^-\): H stays \(+1\), Cl stays \(-1\), O stays \(-2\). It is only a proton transfer (acid-base).
Final Answer:
Reaction (D) involves no change in oxidation number, so it is not a redox reaction. Option (D). \[ \boxed{\text{(D)}} \]
A redox reaction has a change in oxidation number of at least one element. If no oxidation numbers change, the reaction is not redox.
Step 2: Detailed Explanation
(A) Cl\(_2\) goes from 0 to \(-1\), and S in SO\(_2\) goes from \(+4\) to \(+6\): redox.
(B) Zn goes from 0 to \(+2\) and Cu goes from \(+2\) to 0: redox.
(C) H goes from 0 to \(+1\) and O goes from 0 to \(-2\): redox.
(D) \(\text{HCl}+\text{H}_2\text{O}\to\text{H}_3\text{O}^++\text{Cl}^-\): H stays \(+1\), Cl stays \(-1\), O stays \(-2\). It is only a proton transfer (acid-base).
Final Answer:
Reaction (D) involves no change in oxidation number, so it is not a redox reaction. Option (D). \[ \boxed{\text{(D)}} \]
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