ConceptConceptDocsDocuments

CAIE IGCSE Chemistry 7.1.2 Acids in terms of their effect on: (a)

Practise using litmus, thymolphthalein and methyl orange colours to recognise acidic solutions such as dilute hydrochloric acid.

Syllabus
2026–2028
Course
Chemistry 0620

Exam points

  • state indicator colours in acids, including methyl orange red and thymolphthalein colourless
  • distinguish acid indicator changes from incorrect alkali changes

7.1.2—Acids in terms of their effect on: (a) question 1

[Maximum number: 1]

Dilute hydrochloric acid reacts with sodium carbonate solution.

2HCl(aq)+Na2CO3(aq)→2NaCl(aq)+H2O(l)+CO2( g)2 \mathrm{HCl}(\mathrm{aq})+\mathrm{Na}_{2} \mathrm{CO}_{3}(\mathrm{aq}) \rightarrow 2 \mathrm{NaCl}(\mathrm{aq})+\mathrm{H}_{2} \mathrm{O}(\mathrm{l})+\mathrm{CO}_{2}(\mathrm{~g})

Dilute hydrochloric acid was titrated with sodium carbonate solution.
- 10.0 cm310.0 \mathrm{~cm}^{3} of 0.100 mol/dm30.100 \mathrm{~mol} / \mathrm{dm}^{3} hydrochloric acid were placed in a conical flask.
- A few drops of methyl orange indicator were added to the dilute hydrochloric acid.
- The mixture was titrated with sodium carbonate solution.
- 16.2 cm316.2 \mathrm{~cm}^{3} of sodium carbonate solution were required to react completely with the acid.

What colour would the methyl orange indicator be in the hydrochloric acid?

All question bank results loaded