Contents
Independent final check
Explain without the key
name / identify / explain
Final check
Tungsten for lamp filaments is made by heating its oxide in hydrogen: WO3 + 3H2 → W + 3H2O. (a) Name WO3, using a Roman numeral. (b) Which substance is reduced? Give a reason. (c) Explain why this is a redox reaction.
name: use the given information. identify: name or select. explain: give reasons and connect them to evidence.
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Scope and sources
Cambridge IGCSE Chemistry 0620 · 2026–2028 v2 · Original learning materials.
Redox (6.4 Core 1 to 5; Supplement 6 to 13): oxidation numbers from Roman numerals, oxidation and reduction as gain and loss of oxygen, of electrons and as changes in oxidation number, oxidising and reducing agents, and the colour tests with acidified potassium manganate(VII) and potassium iodide. Half-equations are in ELYS01, the reactivity series and displacement in REACT01, and the extraction of metals in EXTR01.
Apparatus, amounts and times in the experiment are illustrative. Real practical work follows a teacher-approved safety method.
Official Cambridge syllabus