NEET (UG)

Practice Test 1 — Redox Reactions

12 questions • 18 minutes • auto-graded with full solutions

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Section A — MCQ (Single Correct & Statement-based)

Question 1

Reduction involves the:

Solution: Reduction Is Gain of electrons.

Question 2

The oxidation number of Cr in $\text{K}_2\text{Cr}_2\text{O}_7$ is:

Solution: $2(+1)+2x+7(-2)=0 \Rightarrow x=+6$.

Question 3

In $\text{MnO}_4^- + 8\text{H}^+ + 5e^- \rightarrow \text{Mn}^{2+} + 4\text{H}_2\text{O}$, Mn changes from:

Solution: Mn is $+7$ in $\text{MnO}_4^-$, $+2$ in $\text{Mn}^{2+}$.

Question 4

Statements: (I) An oxidising agent is reduced. (II) A reducing agent is oxidised. Which are correct?

Solution: Both are correct.

Question 5

Hydrogen has oxidation number $-1$ in:

Solution: In metal hydrides H is $-1$.

Question 6

Which reaction is disproportionation?

Solution: Cl goes to both $-1$ and $+1$.

Question 7

The most reactive metal among these (strongest reducing agent) is:

Solution: K is highest in the activity series.

Question 8

The end point in a $\text{KMnO}_4$ titration is marked by:

Solution: First permanent pink = end point (self-indicating).

Section B — Assertion & Reason

Question 9

A: In a redox reaction the oxidising agent is itself reduced.
R: The oxidising agent accepts the electrons lost by the reducing agent.

Solution: Accepting electrons is exactly being reduced — R explains A.

Question 10

A: The decomposition of $\text{CaCO}_3$ to $\text{CaO}$ and $\text{CO}_2$ is not a redox reaction.
R: No element changes its oxidation number during the decomposition.

Solution: Redox requires a change in oxidation number; none occurs, so R explains A.

Question 11

A: Silver cannot displace copper from copper sulphate solution.
R: Silver is less reactive than copper and so is a weaker reducing agent.

Solution: A less reactive metal cannot displace a more reactive metal's ions, so silver fails to displace copper — R correctly explains A.

Question 12

A: $\text{KMnO}_4$ acts as its own indicator in titrations.
R: $\text{KMnO}_4$ is intensely coloured and the first excess drop gives a permanent pink colour.

Solution: Its intense colour and persistent pink end point make it self-indicating — R explains A.