Lesson 18C.3
18C.3 Practical preparation and purification Quiz: Pearson Edexcel Chemistry, Unit 18
20 questions
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Lesson 18C.3, Practical preparation and purification: 20 multiple choice questions for the Pearson Edexcel Chemistry (9CH0), Unit 18: Organic Chemistry III, written with Revision Ninja.
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The 20 questions
-
What is the primary purpose of carrying out recrystallisation on an organic solid?
- Dissolving an acid
- Melting a solid
- Drying a liquid
- Purifying a solid
-
Why is the minimum volume of hot solvent used during recrystallisation?
- To maximise yield
- To speed cooling
- To reduce boiling
- To prevent evaporation
-
What is the main purpose of washing an organic liquid with aqueous sodium hydrogencarbonate?
- Remove organic impurities
- Remove acidic impurities
- Dry the liquid
- Reduce boiling point
-
What is the main purpose of adding anhydrous magnesium sulfate to an organic liquid?
- Remove acidic impurities
- Increase boiling point
- Remove trace water
- Neutralise unreacted alcohol
-
Which technique separates a solute by partitioning it between two immiscible liquids?
- Recrystallisation
- Fractional distillation
- Steam distillation
- Solvent extraction
-
What is the main advantage of heating an organic reaction mixture under reflux?
- Prevents vapour loss
- Increases reaction pressure
- Lowers activation energy
- Removes volatile impurities
-
What does a sharp melting point matching the literature value indicate about a solid?
- High purity
- High moisture content
- Incomplete reaction
- Low yield
-
What does a sharp boiling point matching the literature value indicate about a liquid?
- Presence of solvent
- High purity
- High density
- Low volatility
-
Which technique is used to separate a volatile liquid product from a non-volatile residue?
- Reflux
- Recrystallisation
- Distillation
- Filtration
-
Why is steam distillation used for water-insoluble compounds with high boiling points?
- Prevents thermal decomposition
- Increases reaction rate
- Prevents evaporation
- Increases product yield
-
What is observed when an acidic liquid is neutralised with aqueous sodium hydrogencarbonate?
- Effervescence
- Colour change
- Precipitation
- Temperature drop
-
How are two immiscible liquid layers separated after mixing in a separating funnel?
- Filter under vacuum
- Decant upper layer
- Drain lower layer
- Distil off solvent
-
A recrystallisation starts with 5.00 g of crude solid and gives 4.20 g of pure product. What is the percentage yield?
- 119%
- 84.0%
- 42.0%
- 16.0%
-
A sample melts broadly below its literature value. What does this indicate?
- It decomposed completely
- It is pure
- It is impure
- It contained catalyst
-
What solubility profile must a suitable solvent have for recrystallisation?
- Insoluble hot, insoluble cold
- Soluble hot, insoluble cold
- Soluble hot, soluble cold
- Insoluble hot, soluble cold
-
Which sequence correctly purifies an organic liquid containing an acidic impurity?
- Distil, wash, dry
- Dry, wash, distil
- Filter, dry, wash
- Wash, dry, distil
-
What physical property is measured to assess the purity of a synthesised organic solid?
- Refractive index
- Boiling point
- Melting point
- Density
-
A 5.00 g crude sample gives 3.00 g of pure product. What is the percentage recovery?
- 3.00%
- 40.0%
- 166.7%
- 60.0%
-
What should you do if an organic liquid remains cloudy after adding a drying agent?
- Distil the mixture
- Add distilled water
- Add more drying agent
- Filter immediately
-
What is the primary purpose of using a separating funnel during purification?
- Separate miscible liquids
- Separate immiscible liquids
- Distil volatile fractions
- Remove dissolved solids
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