AQA GCSE Chemistry (8462), Higher tier · Chemical changes › Reactions of acids
Practise Titrations. 19 exam-style questions plus unlimited generated ones on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
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Name the piece of apparatus used to measure exactly 25.0 cm3 of sodium hydroxide solution.
(volumetric) pipette
Name the piece of apparatus used in a titration to add the acid to the alkali a drop at a time near the end point.
burette
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy4 marks
A student used a titration to find the volume of hydrochloric acid needed to neutralise 25.0 cm3 of sodium hydroxide solution.
(a) Name the piece of apparatus used to measure exactly 25.0 cm3 of sodium hydroxide solution.[1]
(b) Name the piece of apparatus used to add the hydrochloric acid.[1]
(c) The student added phenolphthalein indicator to the sodium hydroxide solution. Give the colour change at the end point.[1]
(d) Suggest why universal indicator is not used in titrations.[1]
Show the answer and mark scheme
(a)Answer: (volumetric) pipette
(volumetric) pipette
(b)Answer: burette
burette
(c)Answer: pink to colourless
pink to colourless
(d)
it changes colour gradually (through many colours), so there is no sharp end point
Question 2Medium5 marks
A student carried out a titration to find the volume of sulfuric acid that reacts exactly with 25.0 cm3 of potassium hydroxide solution. The acid was added from a burette to the alkali in a conical flask.
(a) Why did the student rinse the burette with some of the sulfuric acid before filling it?[1]
(b) Why did the student place the conical flask on a white tile?[1]
(c) Why did the student swirl the flask during the titration?[1]
(d) Why did the student add the acid one drop at a time near the end point?[1]
(e) Describe how the student should read the burette.[1]
Show the answer and mark scheme
(a)
to remove any water / other substances that would dilute (or react with) the acid
(b)
so the colour change of the indicator is easier to see
(c)
to mix the acid and alkali (so they react completely)
(d)
so the end point is not overshot / to find the exact volume needed
(e)
with the eye level with the liquid, reading the bottom of the meniscus
Question 3Hard6 marks
A student titrated 25.0 cm3 of potassium hydroxide solution with sulfuric acid. The concentration of the sulfuric acid was 4.90 g/dm3. The mean titre was 17.50 cm3. H2SO4 + 2KOH → K2SO4 + 2H2O Relative atomic masses (Ar): H = 1, O = 16, S = 32, K = 39
(a) Calculate the concentration of the sulfuric acid in mol/dm3.[2]
(b) Calculate the concentration of the potassium hydroxide solution in mol/dm3.[3]
(c) Calculate the concentration of the potassium hydroxide solution in g/dm3.[1]