NECO 2001 Chemistry · Question 35
The oxidation number of X in is
Options
- A.1
- B.-2
- C.3
- D.4
- E.5
Answer: E. 5
Explanation written with AI and checked against the answer key
Analyze the question: We need the oxidation number of X in the ion XO₄³⁻ (like phosphate, PO₄³⁻). Concept: In an ion, the sum of the oxidation numbers of all atoms equals the charge on the ion. Oxygen usually has an oxidation number of -2 (except in peroxides and similar compounds). Solution: Let the oxidation number of X = x. x + 4(-2) = -3 x - 8 = -3 x = -3 + 8 x = +5 Answer: The oxidation number of X is +5, which is option E. Tip: For ions like PO₄³⁻, AsO₄³⁻ and VO₄³⁻, the central atom is +5. Always use the equation: (sum of oxidation numbers) = charge on the ion. Then substitute oxygen = -2 and solve for the unknown.AI can make mistakes. Report anything that looks wrong.
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