CAIE IGCSE Chemistry 7.1.5 Alkalis in Terms of Their Effect on Questions

Use characteristic indicator colours to identify alkaline solutions, including blue litmus, yellow methyl orange and blue thymolphthalein.

Exam points

state that red litmus changes to blue and blue litmus remains blue in an alkaline solution
state that methyl orange appears yellow in an alkaline solution
state that thymolphthalein is blue in alkali but colourless in acidic solution
use litmus, methyl orange, thymolphthalein and universal-indicator observations to classify alkalis

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Solid sodium hydroxide is a base which dissolves to form an aqueous solution, NaOH(aq).

State the colour of thymolphthalein in NaOH(aq).

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