12.2

Separation and purification

Cambridge IGCSE Chemistry (0620)  · Unit 12: Experimental techniques and chemical analysis  · 6 flashcards

Separation and purification is topic 12.2 in the Cambridge IGCSE Chemistry (0620) syllabus , positioned in Unit 12 — Experimental techniques and chemical analysis , alongside Experimental design and Identification of ions and gases.  In one line: Titration involves gradually adding an acid to a base (or vice versa) of known concentration to react with a base (or acid) of unknown concentration until the reaction is complete. This allows determination of the unknown concentration.

This topic is examined in Paper 1 (multiple-choice) and Papers 3/4 (theory), plus Paper 5 or Paper 6 (practical / alternative to practical).

The deck below contains 6 flashcards — 1 definition and 1 identification card — covering the precise wording mark schemes reward.  Use the definition card to lock down command-word answers (define, state), then move on to the concept and application cards to handle explain, describe and compare questions.

Key definition

Describe the general process of acid-base titration

Titration involves gradually adding an acid to a base (or vice versa) of known concentration to react with a base (or acid) of unknown concentration until the reaction is complete. This allows determination of the unknown concentration.

What the Cambridge 0620 syllabus says

Official 2026-2028 spec

These are the exact learning objectives Cambridge sets for this topic. Match the command word (Describe, Explain, State, etc.) in your answer to score full marks.

  1. Describe Describe an acid-base titration to include the use of a:
  2. Describe Describe how to identify the end-point of a titration using an indicator
Definition Flip

Describe the general process of acid-base titration.

Answer Flip

Titration involves gradually adding an acid to a base (or vice versa) of known concentration to react with a base (or acid) of unknown concentration until the reaction is complete. This allows determination of the unknown concentration.

Key Concept Flip

How do you identify the endpoint of a titration using an indicator?

Answer Flip

The endpoint is identified by a sharp color change of the indicator. Choose an indicator that changes color at or near the equivalence point of the reaction.

Example: methyl orange turns from red to yellow as the solution changes from acidic to alkaline.
Key Concept Flip

In a titration, 20.0 cm³ of 0.0500 mol/dm³ HCl reacts completely with 25.0 cm³ of Ca(OH)₂ solution. Calculate the moles of HCl used.

Answer Flip

Moles of HCl = (Volume of HCl in dm³ * Concentration of HCl in mol/dm³) = (20.0/1000) * 0.0500 = 0.001 mol.

Key Concept Flip

If 0.001 mol of HCl reacted completely with Ca(OH)₂, and 2 moles of HCl react with every 1 mole of Ca(OH)₂, how many moles of Ca(OH)₂ were present?

Answer Flip

Moles of Ca(OH)₂ = Moles of HCl / 2 = 0.001 / 2 = 0.0005 mol. The balanced equation is: 2HCl + Ca(OH)₂ -> CaCl₂ + 2H₂O

Key Concept Flip

Given 0.0005 mol of Ca(OH)₂ in 25.0 cm³ of solution, calculate the concentration of Ca(OH)₂ in mol/dm³.

Answer Flip

Concentration of Ca(OH)₂ = (Moles of Ca(OH)₂ / Volume of Ca(OH)₂ in dm³) = 0.0005 / (25.0/1000) = 0.02 mol/dm³.

Key Concept Flip

The concentration of a solution is 0.02 mol/dm³. Given the Mr of Ca(OH)₂ = 74, calculate the concentration in g/dm³.

Answer Flip

Concentration of Ca(OH)₂ in g/dm³ = (Concentration in mol/dm³ * Mr of Ca(OH)₂) = 0.02 * 74 = 1.48 g/dm³.

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12.1 Experimental design 12.3 Identification of ions and gases

Key Questions: Separation and purification

Describe the general process of acid-base titration.

Titration involves gradually adding an acid to a base (or vice versa) of known concentration to react with a base (or acid) of unknown concentration until the reaction is complete. This allows determination of the unknown concentration.

More topics in Unit 12 — Experimental techniques and chemical analysis

Separation and purification sits alongside these Chemistry decks in the same syllabus unit. Each uses the same spaced-repetition system, so progress in one informs the next.

12.1 Experimental design

12 flashcards
12.3 Identification of ions and gases

11 flashcards

Cambridge syllabus keywords to use in your answers

These are the official Cambridge 0620 terms tagged to this section. Mark schemes credit responses that use the exact term — weave them into your answers verbatim rather than paraphrasing.

separation purification filtration evaporation crystallisation distillation fractional distillation chromatography paper chromatography Rf value pure impure melting point

Key terms covered in this Separation and purification deck

Every term below is defined in the flashcards above. Use the list as a quick recall test before your exam — if you can't define one of these in your own words, flip back to that card.

Describe the general process of acid-base titration

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How to study this Separation and purification deck

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