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Hint : In peroxide, the oxidation state of oxygen is -1. \(x = {-b \pm \sqrt{b^2-4ac} \over 2a}\) Explanation: Oxidation state (or oxidation number) can be calculated by following a set of standard rules: (i) The oxidation state of a monoatomic ion is equal to its charge. (ii) Group 1 (alkali metals) always has an oxidation state of +1; Group 2 (alkaline earth metals) are always +2. (iii) Hydrogen is +1 (except when bonded to metals in hydrides, where it is -1). (iv) Fluorine is always -1; other halogens are usually -1 unless bonded to oxygen or more electronegative halogens. (v) The sum of oxidation states in a neutral compound is zero; in a polyatomic ion, it equals the ion's charge. (vi) Oxygen is usually -2 (except in peroxides, where it is -1, and in superoxides, it is -1/2 and in compounds with fluorine). The oxidation states of the underlined atoms in the given compounds are as follows: S.No. Compound Oxidation state calculation Oxidation state (x) 1 \(\underline KO_2\) \(x + 2(\frac {-1}{2}) = 0\) +1 2 \( H_2 \underline O_2\) \( 2 (+1)\ + 2x = 0\) -1 3 \(H_2 \underline SO_4\) \( 2 (+1)\ + x + 4(-2) = 0\) +6 Hence, option 3 is the correct answer.

Introduction To Redox And Oxidation Number

01

PYQ 2012

easy

chemistry ID: neet-201

N_{2} H_{4}

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(1)

2

(2)

3

(3)

4

(4)

02

PYQ 2019

easy

chemistry ID: neet-201

The correct structure of tribromo octoxide is: 1. 2. 3. 4.

1

(1)

2

(2)

3

(3)

4

(4)

03

PYQ 2019

easy

chemistry ID: neet-201

2 {Cu}^{+}

1

(1)

2

(2)

3

(3)

4

(4)

04

PYQ 2020

easy

chemistry ID: neet-202

The incorrect oxidation number of the underlined atom in the following species is: 1. Cu 2 O is -1 2. Cl is +5 3. K 2 Cr 2 O 7 is +6 4. H Au Cl 4 is +3

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(1)

2

(2)

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(3)

4

(4)

05

PYQ 2022

easy

chemistry ID: neet-202

Identify the incorrect statement from the following: 1. Lithium is the strongest reducing agent among the alkali metals. 2. Alkali metals react with water to form their hydroxides. 3. The oxidation number of K in KO 2 is +4. 4. Ionisation enthalpy of alkali metals decreases from top to bottom in the group.

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(1)

2

(2)

3

(3)

4

(4)

06

PYQ 2024

easy

chemistry ID: neet-202

Which reaction is NOT a redox reaction? 1. 2. 3. 4.

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(1)

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(2)

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(3)

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(4)

07

PYQ 2025

medium

chemistry ID: neet-202

Consider the following compounds: and The oxidation states of the underlined elements in them are, respectively: 1. +1, -2 and +4 2. +4 , -4 and +6 3. +1, -1 and +6 4. +2, -2 and +6

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(1)

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(2)

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(3)

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(4)

(a)	$2 {Cu}^{+}$ $\to$ ${Cu}^{2 +} + {Cu}^{0}$
(b)	$3 {MnO}_{4}^{2 -} + 4 H^{+}$ $\to$ $2 {MnO}_{4}^{-} + {MnO}_{2} + 2 H_{2} O$
(c)	$2 {KMnO}_{4}$ $\overset{∆}{\to}$ $K_{2} {MnO}_{4} + {MnO}_{2} + O_{2}$
(d)	$2 {MnO}_{4}^{-} + 3 {Mn}^{2 +} + 2 H_{2} O$ $\to$ $5 {MnO}_{2} + 4 H^{\oplus}$

Introduction To Redox And Oxidation Number

High-Yield Trend

Questions
7 MCQs

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1.	(a) and (d) only	2.	(a) and (b) only
3.	(a), (b) and (c)	4.	(a), (c) and (d)

1.	Cu₂O is -1	2.	Cl $O_%7B3%7D%5E%7B-%7D$ is +5
3.	K₂Cr₂O₇ is +6	4.	HAuCl₄ is +3

1.	Lithium is the strongest reducing agent among the alkali metals.
2.	Alkali metals react with water to form their hydroxides.
3.	The oxidation number of K in KO₂ is +4.
4.	Ionisation enthalpy of alkali metals decreases from top to bottom in the group.

S.No.	Compound	Oxidation state calculation	Oxidation state (x)
1	$%5Cunderline%20KO_2$	$x%20%2B%202(%5Cfrac%20%7B-1%7D%7B2%7D)%20%3D%200$	+1
2	$H_2%20%5Cunderline%20O_2$	$2%20(%2B1)%5C%20%2B%202x%20%3D%200$	-1
3	$H_2%20%5Cunderline%20SO_4$	$2%20(%2B1)%5C%20%2B%20x%20%2B%204(-2)%20%3D%200$	+6

1.	$N_{2} H_{4}$	2.	${NH}_{3}$
3.	$N_{3} H$	4.	${NH}_{2} OH$

Introduction To Redox And Oxidation Number

High-Yield Trend

Questions 7 MCQs

Official Solution

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Questions
7 MCQs