NEET 2026 ALL Q #1980
COMPETENCY BASED
APPLY
4 Marks 2026 NTA-RE-NEET-2026 MCQ SINGLE
The correct decreasing order of oxidation state of the underlined atom in each molecule is
(A) $\underline{P}_{4}O_{6}>\underline{Cl}_{2}O_{7}>\underline{Al}H_{3}$
(B) $\underline{P}_{4}O_{10}>\underline{S}O_{3}>H_{2}\underline{O}$
(C) $\underline{N}_{2}O_{5}>\underline{Al}_{2}O_{3}>H_{2}\underline{S}$
(D) $\underline{Pb}O_{2}>\underline{N}_{2}O_{3}>\underline{S}O_{3}$
Correct Answer: C

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Detailed Solution

Step 1: Calculate Oxidation States for Option (A)

In $P_4O_6$, $4x + 6(-2) = 0 \implies x = +3$. In $Cl_2O_7$, $2x + 7(-2) = 0 \implies x = +7$. In $AlH_3$, $x + 3(-1) = 0 \implies x = -3$. Order: $+7 > +3 > -3$. Option (A) is incorrect.

Step 2: Calculate Oxidation States for Option (B)

In $P_4O_{10}$, $4x + 10(-2) = 0 \implies x = +5$. In $SO_3$, $x + 3(-2) = 0 \implies x = +6$. In $H_2O$, $2(+1) + x = 0 \implies x = -2$. Order: $+6 > +5 > -2$. Option (B) is incorrect.

Step 3: Calculate Oxidation States for Option (C)

In $N_2O_5$, $2x + 5(-2) = 0 \implies x = +5$. In $Al_2O_3$, $2x + 3(-2) = 0 \implies x = +3$. In $H_2S$, $2(+1) + x = 0 \implies x = -2$. Order: $+5 > +3 > -2$. This matches the decreasing order.

Step 4: Calculate Oxidation States for Option (D)

In $PbO_2$, $x + 2(-2) = 0 \implies x = +4$. In $N_2O_3$, $2x + 3(-2) = 0 \implies x = +3$. In $SO_3$, $x + 3(-2) = 0 \implies x = +6$. Order: $+6 > +4 > +3$. Option (D) is incorrect.

Final Answer: (C)

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Pedagogical Audit
Bloom's Analysis: This is an APPLY question because the student must utilize the rules of oxidation number calculation to evaluate multiple chemical species and compare their values.
Knowledge Dimension: PROCEDURAL
Justification: The question requires the application of a specific algorithm (algebraic sum of oxidation states) to solve a problem.
Syllabus Audit: In the context of NEET, this is classified as COMPETENCY. It tests the student's ability to perform rapid calculations and logical ordering, which is essential for competitive chemistry exams.