Which of the following reactions is NOT a redox reaction?
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Correct answer
C. AgNO3 + NaCl → AgCl + NaNO3
Principle or equation
A redox reaction involves a change in oxidation states of elements. If no element changes oxidation state, the reaction is not redox.
Why this answer is correct
In AgNO3 + NaCl → AgCl + NaNO3, all oxidation states remain unchanged: Ag +1, N +5, O -2, Na +1, Cl -1. This is a double displacement (metathesis) reaction, not redox. The others involve changes: hydrogen peroxide decomposes (O changes from -1 to 0 and -2), zinc displaces copper (Zn 0 to +2, Cu +2 to 0), potassium chlorate decomposes (Cl +5 to -1, O -2 to 0).
Example
In the reaction CuO + H2 → Cu + H2O, copper goes from +2 to 0 and hydrogen from 0 to +1, so it is redox.
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