Titration

OCR

GCSE

Titration is a quantitative analytical technique used to determine the unknown concentration of a solution by reacting it with a standard solution of known concentration. The process relies on the precise measurement of liquid volumes using volumetric apparatus, specifically burettes and pipettes, to reach a neutralization end-point signaled by an indicator. Mastery of this topic requires the synthesis of practical precision, specifically obtaining concordant results, with advanced stoichiometric calculations involving mole ratios and unit conversions between cubic centimetres and cubic decimetres.

Objectives

Exam Tips

Pitfalls

Key Terms

Mark Points

What You Need to Demonstrate

Key skills and knowledge for this topic

Award 1 mark for calculating the number of moles of the known substance using n = c × v (ensure volume is converted to dm³).
Credit the selection of concordant titres (within 0.10 cm³) for the calculation of the mean titre.
Award 1 mark for applying the correct mole ratio from the balanced symbol equation to determine moles of the unknown.
Credit the explanation that a white tile is used to clearly identify the end-point colour change.
Award 1 mark for stating that the burette is used for variable volumes and the pipette for fixed volumes.

Example Examiner Feedback

Real feedback patterns examiners use when marking

"You correctly calculated the moles, but you forgot to apply the mole ratio from the equation."
"Excellent definition of the end-point, but remember to specify that Universal Indicator is not suitable here."
"Your calculation of the mean is incorrect because you included the rough titre; only use concordant results."
"Good use of terminology like 'meniscus' and 'concordant'; to improve, ensure you show the conversion of cm³ to dm³ explicitly."

Marking Points

Key points examiners look for in your answers

Award 1 mark for calculating the number of moles of the known substance using n = c × v (ensure volume is converted to dm³).
Credit the selection of concordant titres (within 0.10 cm³) for the calculation of the mean titre.
Award 1 mark for applying the correct mole ratio from the balanced symbol equation to determine moles of the unknown.
Credit the explanation that a white tile is used to clearly identify the end-point colour change.
Award 1 mark for stating that the burette is used for variable volumes and the pipette for fixed volumes.

Examiner Tips

Expert advice for maximising your marks

💡When calculating the mean titre, explicitly state which values you are using (e.g., 'Titres 2 and 3 are concordant') to secure method marks.
💡In 6-mark method descriptions, specify adding the titrant 'dropwise' near the end-point and 'swirling' the flask to access top-band descriptors.
💡If the question asks for concentration in g/dm³, calculate in mol/dm³ first and then multiply by the relative formula mass (Mr).

Common Mistakes

Pitfalls to avoid in your exam answers

Failing to convert volumes from cm³ to dm³ by dividing by 1000, resulting in calculation errors by a factor of 1000.
Including the 'rough' titre or non-concordant results when calculating the mean volume, which incurs accuracy penalties.
Suggesting Universal Indicator is suitable for titrations; examiners reject this as it does not provide a sharp end-point.
Inverting the concentration formula to volume ÷ moles instead of moles ÷ volume.

Key Terminology

Essential terms to know

Volumetric analysis and apparatus precision

Stoichiometric calculations and mole ratios

Indicators and end-point determination

Preparation of standard solutions

Concordancy and error analysis

Likely Command Words

How questions on this topic are typically asked

Calculate

Describe

Explain

Suggest

Determine

Practical Links

Related required practicals

•{"code":"PAG C2","title":"Titration","relevance":"Determination of reacting volumes of strong acid and strong alkali"}

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