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A colourless solution W turns thymolphthalein blue. Fill in the gaps. Solution W is an alkali, so it contains (1) ___ ions. It turns litmus (2) ___ and methyl orange (3) ___. Its pH is (4) ___ 7.
state: give a concise answer.
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Scope and sources
Cambridge IGCSE Chemistry 0620 · 2026–2028 v2 · Original learning materials.
The characteristic properties of acids and bases (7.1 Core 1 to 8; Supplement 9 to 12): indicator colours, acids and bases with metals, bases, carbonates and ammonium salts, H⁺ and OH⁻ ions, the pH scale and universal indicator, neutralisation, proton donors and acceptors, and strong and weak acids. Acidic, basic and amphoteric oxides are in the module Oxides, preparing salts in Making salts and titration in Titration.
Apparatus, amounts and times in the experiment are illustrative. Real practical work follows a teacher-approved safety method.
Official Cambridge syllabus