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Edexcel A-Level Chemistry AS 8.3 Indicate the Oxidation Number of an Element in a Compound or an Ion Questions

Calculate the central element's oxidation state from the formula and charge, then write that value as a Roman numeral rather than an ionic charge.

Syllabus
First assessment 2019
Course
Chemistry YCH11
Level
AS

Exam points

  • Interpret a Roman numeral as the named element's oxidation number, not an ion charge.
  • Name chlorate or sulfate species by calculating and writing the correct Roman numeral.

Edexcel A-Level Chemistry AS 8.3 Indicate the Oxidation Number of an Element in a Compound or an Ion Questions question 1

[Maximum number: 1]

Chlorine dioxide, ClO2\mathrm{ClO}_{2}, can be used to treat water to make it safe for drinking. The molecule is a free radical. One suggested structure is shown.

Figure for Question Edexcel A-Level Chemistry AS 8.3 Indicate the Oxidation Number of an Element in a Compound or an Ion Questions question 1 — Edexcel A-Level Chemistry AS

Chlorine dioxide can be made from potassium chlorate(V), KClO3\mathrm{KClO}_{3}, in a two-step process.

Step 1 Potassium chlorate(V) reacts with concentrated sulfuric acid to form compound A.

Step 2 Compound A then undergoes a disproportionation reaction to form chlorine dioxide and hydrogen chlorate(VII), HClO4\mathrm{HClO}_{4}.

State the meaning of the Roman numerals in chlorate(V) and chlorate(VII).

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