StemCET Logo

Chemistry Question 53 – NEET-UG 2024

← Back
Which reaction is NOT a redox reaction?

A redox reaction involves a change in the oxidation states of one or more elements.

Step 1: Define Redox Reaction and Oxidation States✦ Active

A redox (reduction-oxidation) reaction is a chemical reaction in which the oxidation states of atoms are changed. Oxidation is the loss of electrons (increase in oxidation state), and reduction is the gain of electrons (decrease in oxidation state). To identify a non-redox reaction, we must check if all elements maintain their oxidation states throughout the reaction.

💡 Teacher's Secret Hint

Remember common oxidation states: alkali metals are +1, alkaline earth metals are +2, oxygen is usually -2 (except in peroxides), and hydrogen is usually +1 (except in metal hydrides).

Step 2: Analyze Oxidation States for Each Reaction○ Expand

Let's determine the oxidation states for each element in all given reactions:

(1) 2KClO3+I2→2KIO3+Cl2

Reactants: K(+1), Cl(+5), O(−2); I(0)

Products: K(+1), I(+5), O(−2); Cl(0)

Changes: Cl changes from +5 to 0 (reduction); I changes from 0 to +5 (oxidation). This is a redox reaction.

(2) H2+Cl2→2HCl

Reactants: H(0); Cl(0)

Products: H(+1), Cl(−1)

Changes: H changes from 0 to +1 (oxidation); Cl changes from 0 to −1 (reduction). This is a redox reaction.

(3) BaCl2+Na2SO4→BaSO4+2NaCl

Reactants: Ba(+2), Cl(−1); Na(+1), S(+6), O(−2)

Products: Ba(+2), S(+6), O(−2); Na(+1), Cl(−1)

Changes: No element changes its oxidation state. This is a double displacement reaction. Therefore, it is NOT a redox reaction.

(4) Zn+CuSO4→ZnSO4+Cu

Reactants: Zn(0); Cu(+2), S(+6), O(−2)

Products: Zn(+2), S(+6), O(−2); Cu(0)

Changes: Zn changes from 0 to +2 (oxidation); Cu changes from +2 to 0 (reduction). This is a redox reaction.

Step 3: Identify the Non-Redox Reaction○ Expand

Based on the analysis of oxidation states, reaction (3) is the only one where no element undergoes a change in its oxidation state. Thus, it is not a redox reaction.

💡 Teacher's Secret Hint

Double displacement reactions, where ions simply swap partners, are typically non-redox reactions unless one of the products is an elemental substance or involves a change in the polyatomic ion's internal oxidation states (which is rare for common ions like sulfate).

✦ STEM Console utilizes AI models to generate step-by-step explanations and math clues. AI can make mistakes.