Q.95 Chemistry ⭐ 360° Option Elimination Active

NEET 2023 Chemistry Question 95 Solution

Topic: The d- and f-Block Elements · Official NTA Booklet Code G5

Question

Which of the following statements are INCORRECT? A. All the transition metals except scandium form MO oxides which are ionic. B. The highest oxidation number corresponding to the group number in transition metal oxides is attained in Sc₂O₃ to Mn₂O₇. C. Basic character increases from V₂O₃ to V₂O₄ to V₂O₅. D. V₂O₄ dissolves in acids to give VO₄³⁻ salts. E. CrO is basic but Cr₂O₃ is amphoteric. Choose the correct answer from the options given below:

✓

Verified Against NTA Final Answer Key

Option (4) : C and D only

📚 The d- and f-Block Elements Medium

📋 Given Parameters & Problem Setup

Topic evaluated Properties of transition metal oxides (Sc, V, Cr, Mn)

Statements A, B, C, D, E

Question requirement Identify INCORRECT statements

⚡

The 30-Second Exam Hall Shortcut: ⚡ Oxide Oxidation State Trend: Higher Oxidation State = Higher Acidity!

⏱️ Save ~40 seconds

As oxidation number of vanadium increases (+3 in V₂O₃, +4 in V₂O₄, +5 in V₂O₅), basic character DECREASES and acidic character increases (V₂O₃ basic, V₂O₄ amphoteric, V₂O₅ amphoteric/acidic). Hence Statement C is FALSE! Also, V₂O₄ dissolves in acids to give VO²⁺ (vanadyl ion, +4 state), NOT VO₄³⁻ (+5 state). Hence Statement D is FALSE! Statements C and D are INCORRECT ⟹ Option (4)!

1 Check Statement A: All transition metals except Sc form MO oxides which are ionic (Verbatim NCERT, TRUE).

2 Check Statement B: Highest oxidation number in oxides matches group number for Sc₂O₃ (+3) to Mn₂O₇ (+7) (Verbatim NCERT, TRUE).

3 Check Statement C: "Basic character increases from V₂O₃ to V₂O₄ to V₂O₅." False! As oxidation state rises, electronegativity rises, so basic character decreases and acidic character increases (INCORRECT).

4 Check Statement D: "V₂O₄ dissolves in acids to give VO₄³⁻ salts." False! V₂O₄ has vanadium in +4 state and gives VO²⁺ salts; VO₄³⁻ is orthovanadate (+5) (INCORRECT).

5 Check Statement E: CrO is basic, Cr₂O₃ is amphoteric, CrO₃ is acidic (Verbatim NCERT, TRUE).

6 Incorrect statements are C and D only (Option 4).

🛡️

Why You Can 100% Trust This Shortcut: Verbatim NCERT d- and f-Block Elements section on Oxides and Oxoanions of Metals.

📐

Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Evaluate Statements A and B

Statement A: Transition metals (except scandium, which only forms Sc₂O₃) form ionic MO oxides (TiO to NiO) — verbatim NCERT (TRUE). Statement B: Highest oxidation states matching group number occur from Group 3 (Sc₂O₃, +3) to Group 7 (Mn₂O₇, +7) — verbatim NCERT (TRUE):

\text{Statements A and B} \iff \text{Factually True}

Step 2

Evaluate Statement C: Vanadium Oxide Acid-Base Trend

As the oxidation state of a transition metal increases, covalent character increases and basic character decreases: V₂O₃ (+3) is basic, V₂O₄ (+4) is amphoteric, and V₂O₅ (+5) is amphoteric/acidic. Statement C claims basic character increases, which is directly FALSE:

\text{Basic character: } \text{V}_2\text{O}_3 (+3) > \text{V}_2\text{O}_4 (+4) > \text{V}_2\text{O}_5 (+5) \implies \text{Statement C is INCORRECT}

Step 3

Evaluate Statement D: Dissolution Chemistry of V₂O₄

V₂O₄ has vanadium in oxidation state +4. It dissolves in non-oxidizing acids to give vanadyl salts containing VO²⁺ (+4). VO₄³⁻ contains vanadium in oxidation state +5 (orthovanadate). Statement D is FALSE:

\text{V}_2\text{O}_4 + 2\text{H}^+ \longrightarrow 2\text{VO}^{2+} + \text{H}_2\text{O} \quad (\text{VO}^{2+} \text{ salts, NOT } \text{VO}_4^{3-}) \implies \text{Statement D is INCORRECT}

Step 4

Evaluate Statement E: Chromium Oxides

CrO (Cr²⁺) is basic, Cr₂O₃ (Cr³⁺) is amphoteric, and CrO₃ (Cr⁶⁺) is acidic. Statement E correctly identifies CrO as basic and Cr₂O₃ as amphoteric (TRUE):

\text{CrO (basic)}, \quad \text{Cr}_2\text{O}_3 \text{ (amphoteric)} \implies \text{Statement E is True}

⭐

360° Option Elimination Engine Key Feature

Diagnose every choice: Know exactly why the right option works and why distractors fail.

4-Option Deep Scan

1 (1)

✗ Incorrect

Verdict & Scientific Reason:

Statement B is factually true, so it cannot be part of the incorrect set.

⚠️

Student Fallacy (Why candidates pick this trap): Candidate incorrectly thought highest oxidation states do not reach Mn₂O₇.

2 (2)

✗ Incorrect

Verdict & Scientific Reason:

Both Statements A and E are correct NCERT principles.

⚠️

Student Fallacy (Why candidates pick this trap): Candidate confused correct statements with incorrect statements.

3 (3)

✗ Incorrect

Verdict & Scientific Reason:

Statement B is correct.

⚠️

Student Fallacy (Why candidates pick this trap): Candidate failed to verify statement B.

4 (4)

✓ 100% Correct

Verdict & Scientific Reason:

Accurate: Statements C and D are both false statements regarding vanadium oxides.

💡

Why this is airtight: None. Candidate correctly identified the two incorrect statements.

⚠️

NTA Trap Alert: Overlooking Oxidation State Conservation in Acid Dissolution

In V₂O₄, vanadium has oxidation state +4. Dissolution in acid does not oxidize it; it forms the vanadyl cation VO²⁺ (+4). VO₄³⁻ has vanadium in oxidation state +5 (formed by dissolution of V₂O₅ in alkali)!

🛡️ How to avoid the -1 mark: Check oxidation states: V in V₂O₄ is +4 ⟶ forms VO²⁺ (+4). It cannot form VO₄³⁻ (+5) without an oxidizing agent.

📖

Core NEET Syllabus Standard

National Eligibility cum Entrance Test (NEET UG) · The d- and f-Block Elements Standard Benchmark

Core Scientific Principle Tested:

"Basic character decreases as oxidation state increases; V₂O₄ dissolves in acid to yield VO²⁺ salts."

Syllabus Focus: Transition Metal Oxides and Oxoanions – Acid-Base Trends

Preserved in Rationalized Curriculum Syllabus & Academic Standards ↗

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NEET 2023 Chemistry Question 95 Solution

Question

The 30-Second Exam Hall Shortcut: ⚡ Oxide Oxidation State Trend: Higher Oxidation State = Higher Acidity!

Step-by-Step Rigorous Workflow & Mathematical Proof

Evaluate Statements A and B

Evaluate Statement C: Vanadium Oxide Acid-Base Trend

Evaluate Statement D: Dissolution Chemistry of V₂O₄

Evaluate Statement E: Chromium Oxides

360° Option Elimination Engine Key Feature

NTA Trap Alert: Overlooking Oxidation State Conservation in Acid Dissolution

Core NEET Syllabus Standard

Ready to attempt under real exam pressure?

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