Making sodium, potassium and ammonium salts
4 marks · NormalWhen using methyl orange during an acid–alkali titration:
State the colour of methyl orange in an alkaline solution.
Describe what you would observe as acid is slowly added to the alkaline solution containing methyl orange.
Explain why methyl orange is suitable for titrations involving strong acids and strong alkalis.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) Yellow · must show yellow
(b) The colour will change from yellow to orange and then to red as more acid is added. · must show yellow to orange to red, sequence of colour change during titration
(c) Because methyl orange gives a clear, sharp colour change at the endpoint for strong acid–strong alkali titrations. · must show sharp colour change, suitable for strong acid–alkali
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Yellow in alkali.
B2a (b) · 1 mark · Indicates colour goes from yellow to orange as acid is added (endpoint).
B2b (b) · 1 mark · Further acid turns solution red (excess acid).
B3 (c) · 1 mark · Mentions methyl orange is suitable for titrations because of sharp/clear colour change at strong acid–strong alkali endpoint.
Worked solution
(a) The colour is yellow in alkaline solution.
(b) As acid is added, the colour changes from yellow to orange (at the endpoint), and then to red if more acid is added.
(c) Methyl orange is suitable because it gives a distinct colour change at the endpoint for titrations involving strong acids and strong alkalis.