CCEA A-Level Chemistry 1110
Formulae, Equations and Amounts of Substance
Atomic Structure
Bonding
Intermolecular Forces and Structure
Shapes of Molecules and Ions
Redox
The Halogens
Acid-Base Titrations
Qualitative Tests
Formulae and Amounts of a Substance
Nomenclature and Isomerism in Organic Chemistry
Alkanes
Alkenes
Halogenoalkanes
Alcohols
Infrared Spectroscopy
Energetics
Kinetics
Equilibrium
Group II Elements and Their Compounds
Lattice Enthalpy, Entropy and Free Energy
Rates of Reaction
Equilibrium and Acid-Base Equilibria
Isomerism
Aldehydes and Ketones
Carboxylic Acids
Derivatives of Carboxylic Acids
Aromatic Chemistry
Spectroscopy and Chromatography
Volumetric Analysis
Transition Metals
Electrode Potentials
Amines
Amides and Polymers
Amino Acids and Proteins
Derivatives of Carboxylic Acids
The laboratory preparation of a liquid ester
- 3 things to know
- Unit A2 1
Overview
Why anti-bumping granules are placed in the flask, why the mixture is heated under reflux and how the two layers are separated after washing.
What you need to know
Answer each one before you reveal it.
Explain why the concentrated sulfuric acid is added slowly with swirling and cooling in a laboratory ester preparation
Describe how the crude ester is removed from the reaction mixture after reflux.
Questions from this subtopic
Each one with the model answer underneath.
- 1
State the three substances mixed in the flask at the start of a laboratory ester preparation.
Model answer
The carboxylic acid, the alcohol and a few drops of concentrated sulfuric acid are mixed together.
- 2
Explain why the concentrated sulfuric acid is added slowly with swirling and cooling.
Model answer
Mixing concentrated sulfuric acid with organic liquids is strongly exothermic, so adding it slowly prevents the mixture from boiling over.
- 3
State why anti-bumping granules are placed in the flask.
Model answer
They provide nucleation sites so the liquid boils smoothly rather than surging.
- 4
Explain why the mixture is heated under reflux.
Model answer
Reflux allows the mixture to be kept at its boiling point for a long time without any of the volatile reactants or products escaping.
- 5
Describe how the crude ester is removed from the reaction mixture after reflux.
Model answer
The apparatus is rearranged for distillation and the ester is distilled off, being collected over a narrow range around its boiling point.
- 6
Name the reagent used to wash the crude distillate and state what it removes.
Model answer
Sodium carbonate solution is used, and it neutralises and removes the unreacted carboxylic acid and any sulfuric acid carried over.
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