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
Acid-Base Titrations
Indicators and the end point
- 3 things to know
- Unit AS 1
Overview
End point of a titration, colours of phenolphthalein in acid and in alkali and colours of methyl orange in acid and in alkali.
What you need to know
Answer each one before you reveal it.
What is meant by the end point of a titration?
Why is only a few drops of indicator added to the conical flask?
Questions from this subtopic
Each one with the model answer underneath.
- 1
What is meant by the end point of a titration?
Model answer
The end point is the moment at which the indicator changes colour permanently, marking the completion of the reaction.
- 2
Why is only a few drops of indicator added to the conical flask?
Model answer
An indicator is itself a weak acid or base, so adding more than a few drops would react with a measurable amount of the solution being titrated.
- 3
State the colours of phenolphthalein in acid and in alkali.
Model answer
Phenolphthalein is colourless in acid and pink in alkali.
- 4
State the colours of methyl orange in acid and in alkali.
Model answer
Methyl orange is red in acid and yellow in alkali.
- 5
Describe the colour seen at the end point when methyl orange is used.
Model answer
The solution turns from yellow to the first permanent orange as the acid is added.
- 6
Describe the colour change seen at the end point when alkali is run into an acid containing phenolphthalein.
Model answer
The colourless solution turns to the first permanent pale pink.
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