GCSE Chemistry · Required practical · Triple only

Titration lab

Carry out a real titration between sodium hydroxide and sulfuric acid. Choose what goes in the burette and the flask, pick an indicator, then add solution until the indicator changes colour. Record your readings, find concordant results and work out the unknown concentration.

GCSE ChemistryRequired practicalConcentration calculations: Higher tier
In the burette
Unknown concentration
Indicator
2NaOH + H₂SO₄ → Na₂SO₄ + 2H₂O
Burette close-up Read the bottom of the meniscus, at eye level. Burettes are read to the nearest 0.05 cm³.

Keyboard: hold F to run fast, press D for one drop, S to swirl.

Results

Your results table

Write down each burette reading yourself from the close-up. The titre is worked out from your readings.

TitrationInitial reading / cm³Final reading / cm³Titre / cm³
Calculation HT

Work out the unknown concentration

Use your mean titre. Each step is checked against your own numbers, so a wrong titre won't stop you getting the method right.

How close did you get?
The true value stays hidden until you reveal it.
Method and theory

What you need to know

Method

  1. Use a pipette and pipette filler to put 25.0 cm³ of one solution into a conical flask.
  2. Add a few drops of indicator and stand the flask on a white tile.
  3. Fill the burette with the other solution and record the initial reading.
  4. Add the solution from the burette, swirling the flask. Near the end point, add it drop by drop.
  5. Stop when the indicator changes colour permanently. Record the final reading.
  6. Repeat until you have concordant results (within 0.10 cm³ of each other). Calculate the mean.

Why each step matters

  • White tile: makes the colour change easier to see.
  • Swirling: mixes the solutions so the colour change is accurate.
  • Drop by drop near the end: so you don't overshoot the end point.
  • Rough titration first: shows roughly where the end point is.
  • Read the bottom of the meniscus at eye level: avoids reading errors.
  • Repeat for concordant results: makes the result more reliable.

Indicator colours

IndicatorIn acidIn alkali
Methyl orange Red Yellow
Phenolphthalein Colourless Pink

Universal indicator is not used because it changes colour gradually, so there is no sharp end point.

The reaction

2NaOH + H₂SO₄ → Na₂SO₄ + 2H₂O

This is neutralisation. The ionic equation is H⁺ + OH⁻ → H₂O.

Sulfuric acid releases two H⁺ ions per formula, so 2 mol of sodium hydroxide react with 1 mol of sulfuric acid. Forgetting this 2 : 1 ratio is the most common calculation mistake.

Relative formula masses: NaOH = 40, H₂SO₄ = 98.

Check understanding

Quick quiz

Longer answers

Exam-style questions: 10 questions

They start easy and get harder. Write your answer first, then check it.