Required practical: Acid–alkali titration to find an unknown concentration

Aim

To find the concentration of an acid or alkali by titrating against a standard solution, using a suitable indicator and correct technique.

Method (step-by-step)

1. Rinse glassware appropriately (pipette with solution, burette with acid/alkali).
2. Fill the burette, record initial volume, pipette a known volume of one solution into a flask.
3. Add indicator; run in the other solution from the burette slowly with swirling until the endpoint.
4. Record final burette reading; repeat until concordant titres (±0.1 cm³).
5. Calculate unknown concentration using n₁V₁ = n₂V₂ logic with balanced moles.

Equipment

• Burette, pipette, filler
• conical flask
• white tile
• standard solutions
• indicator

Variables

• Independent: Not applicable in a standardisation titration — you match moles at endpoint.
• Dependent: Titre volume (cm³) to reach endpoint.
• Control: Same indicator; same volumes pipetted; consistent endpoint judgement

Results & analysis

Use mean titre from concordant results only; propagate uncertainty if asked (± half smallest division).

Graphs & interpretation

Usually not a graph practical — but pH curves may appear at A-level; at GCSE focus on titre accuracy.

Exam-style question prompts

• Describe how you would carry out a titration safely.
• Why are titres repeated until concordant?

Exam tips

• Moles = concentration × volume(dm³)
• Washings: reduce systematic error

Related topic revision

• Concentration of solutions
• pH and neutralisation