Oxides of Transition Metals NEET 2023: Full Solution

What did the Oxides of Transition Metals NEET 2023 question ask?

The oxides of transition metals NEET 2023 question has one definite answer: statements C and D are incorrect, so select option (3). Solving it requires two checks, oxidation state and oxide character or reaction product. The stem asks for the incorrect statements, so the final polarity check matters.

This was a NEET UG 2023 Chemistry question from 7 May 2023, slot E1, from the chapter d- and f-Block Elements. Its question-bank difficulty tier is hard, with an expected solving time of 90 seconds based on the question-bank classification.

In fresh wording, the five statements were:

A: Except scandium, transition metals form ionic oxides of the MO type.
B: In Sc₂O₃, TiO₂, V₂O₅, CrO₃ and Mn₂O₇, the metal oxidation states match group numbers 3 through 7.
C: Basic character increases across V₂O₃, V₂O₄ and V₂O₅.
D: When V₂O₄ dissolves in acid, it produces salts containing VO₄³⁻.
E: CrO is basic, while Cr₂O₃ is amphoteric.

The task is to identify the incorrect statements, not the correct statements. The answer combinations were:

Which two checks are needed before testing the statements?

Use two checks for every oxide. First, calculate the metal oxidation state by assigning oxygen an oxidation number of −2. Second, connect that oxidation state with basic, amphoteric or acidic character. For a reaction product, confirm that the metal oxidation state remains unchanged unless a redox process is explicitly stated.

How do you calculate the oxidation state in a neutral oxide?

The sum of oxidation numbers in a neutral oxide is zero. Represent the metal oxidation state by x, multiply each oxidation number by the number of atoms, and solve. This prevents errors when the oxide contains more than one metal or oxygen atom.

For a general MO oxide:

x + (- 2) = 0

x = + 2

For an oxide such as M₂O₅:

2 x + 5 (- 2) = 0

x = + 5

How does oxidation state control oxide character?

For oxides of the same transition metal, a higher metal oxidation state generally means lower basic character and higher acidic character. Low oxidation-state oxides tend to be basic, intermediate oxides may be amphoteric, and high oxidation-state oxides tend to be acidic.

Keep oxide character separate from reaction product:

Low oxidation state: Usually basic
Intermediate oxidation state: May be amphoteric
High oxidation state: Usually acidic
Acid-base reaction: Does not change the metal oxidation state unless redox is involved

Before marking the answer, apply one final instruction-word check:

Required set = INCORRECT statements

How do you evaluate statements A to E?

Statements A, B and E are correct. Statements C and D are incorrect. The official statement-by-statement method is safer than trying to match an option from memory because it checks both the chemistry and the instruction word.

Why is statement A correct?

In an MO oxide, oxygen has oxidation number −2, so the metal must be in the +2 oxidation state. Transition metals except scandium form ionic MO-type oxides. Both the oxidation-state calculation and the stated exception therefore support statement A.

x + (- 2) = 0

x = + 2

Statement A is correct.

Why is statement B correct?

The metals in Sc₂O₃, TiO₂, V₂O₅, CrO₃ and Mn₂O₇ have oxidation states +3, +4, +5, +6 and +7 respectively. These match group numbers 3 through 7, so the full sequence supports statement B.

S c_{2} O_{3} : 2 x + 3 (- 2) = 0 \Rightarrow x = + 3

T i O_{2} : x + 2 (- 2) = 0 \Rightarrow x = + 4

V_{2} O_{5} : 2 x + 5 (- 2) = 0 \Rightarrow x = + 5

C r O_{3} : x + 3 (- 2) = 0 \Rightarrow x = + 6

M n_{2} O_{7} : 2 x + 7 (- 2) = 0 \Rightarrow x = + 7

Statement B is correct.

Why is statement C incorrect?

Vanadium has oxidation states +3, +4 and +5 in V₂O₃, V₂O₄ and V₂O₅ respectively. As the oxidation state rises, acidic character increases and basic character decreases. The statement claims the opposite trend, so it is false.

V_{2} O_{3} : 2 x + 3 (- 2) = 0 \Rightarrow x = + 3

V_{2} O_{4} : 2 x + 4 (- 2) = 0 \Rightarrow x = + 4

V_{2} O_{5} : 2 x + 5 (- 2) = 0 \Rightarrow x = + 5

The correct trend is an increase in acidic character, not basic character. Statement C is incorrect.

Why is statement D incorrect?

Vanadium is +4 in V₂O₄ and remains +4 in VO²⁺. In VO₄³⁻, however, vanadium is +5. Because no redox process is stated, dissolution in acid must not change vanadium from +4 to +5.

For V₂O₄:

2 x + 4 (- 2) = 0 \Rightarrow x = + 4

For VO²⁺:

x + (- 2) = + 2 \Rightarrow x = + 4

For VO₄³⁻:

x + 4 (- 2) = - 3

x - 8 = - 3 \Rightarrow x = + 5

V₂O₄ dissolves in acid to form VO²⁺ salts. The balanced reaction conserves atoms and charge:

V_{2} O_{4} + 4 H^{+} \to 2 V O^{2 +} + 2 H_{2} O

Statement D is incorrect.

Why is statement E correct?

CrO contains chromium in the low +2 oxidation state and is basic. Cr₂O₃ contains chromium in the intermediate +3 oxidation state and is amphoteric. The oxidation-state trend therefore agrees with both classifications in statement E.

For CrO:

x + (- 2) = 0 \Rightarrow x = + 2

For Cr₂O₃:

2 x + 3 (- 2) = 0 \Rightarrow x = + 3

Statement E is correct.

The compact audit is:

A: Correct
B: Correct
C: Incorrect
D: Incorrect
E: Correct

The final answer to the oxides of transition metals NEET 2023 question is statements C and D only. This is option (3), labelled answer choice C in the supplied option list.

Why does selecting A and E give the wrong answer?

A student may classify A and E correctly but forget that the stem asks for the incorrect statements. Selecting A and E then reports the two correct statements instead of the required two incorrect statements. This is a question-polarity error, not a chemistry-content error.

Use this one-line filter before marking the OMR:

Required = incorrect; my set = C, D.

Do not confuse statement C with answer choice C. The incorrect statement pair C and D corresponds to option (3), which is labelled answer choice C.

For more OMR-specific process checks, see how to choose a NEET mock test app for OMR practice.

Which three related d-block questions should you solve next?

These three questions apply the same audit: calculate the metal oxidation state, then check oxide character or the reaction product. The oxidation-state calculation should come before any memorised label because it gives the reason for the classification.

How should V₂O₃, V₂O₄ and V₂O₅ be arranged in increasing acidic character?

The increasing order of acidic character is V₂O₃, V₂O₄ and V₂O₅. Vanadium has oxidation states +3, +4 and +5 respectively. As its oxidation state increases, acidic character increases and basic character decreases.

V_{2} O_{3} < V_{2} O_{4} < V_{2} O_{5}

How are CrO, Cr₂O₃ and CrO₃ classified?

CrO is basic, Cr₂O₃ is amphoteric, and CrO₃ is acidic. Their chromium oxidation states are +2, +3 and +6 respectively. The increasing oxidation state changes the oxide character from basic to amphoteric to acidic.

CrO: Basic, chromium is +2
Cr₂O₃: Amphoteric, chromium is +3
CrO₃: Acidic, chromium is +6

Which vanadium ion forms when V₂O₄ dissolves in acid?

The ion formed is VO²⁺, with vanadium remaining in the +4 oxidation state. Vanadium is +4 in both V₂O₄ and VO²⁺, so the acid-base reaction preserves its oxidation state rather than producing the +5 state found in VO₄³⁻.

V O^{2 +}

For every related oxide question, write the metal oxidation state beside each species before classifying the oxide or checking the product.

Frequently asked questions

What is the correct answer to the oxides of transition metals NEET 2023 question?

Statements C and D are incorrect. Therefore, the correct answer is option (3), labelled answer choice C in the given option list.

Why is statement C incorrect in the NEET 2023 question?

Vanadium has oxidation states +3, +4 and +5 in V₂O₃, V₂O₄ and V₂O₅ respectively. As oxidation state increases, acidic character increases and basic character decreases, contrary to statement C.

Which ion forms when V₂O₄ dissolves in acid?

V₂O₄ forms VO²⁺ salts when it dissolves in acid. Vanadium remains in the +4 oxidation state because no redox process is involved.

How does oxidation state affect transition-metal oxide character?

Low oxidation-state oxides are generally basic, intermediate oxides may be amphoteric, and high oxidation-state oxides are usually acidic. For oxides of the same metal, increasing oxidation state normally increases acidic character.

Oxides of Transition Metals NEET 2023: Why C and D Are Incorrect