Preparing Esters
This practical lesson covers:
- How to prepare a sample of an ester such as ethyl ethanoate
Preparation of ethyl ethanoate
Aim
To prepare a sample of an ester such as ethyl ethanoate.
Background information
Esters are formed through a reaction between an alcohol and a carboxylic acid in the presence of a concentrated acid catalyst, usually sulfuric acid. This process is called esterification. In this practical, you will prepare a sample of ethyl ethanoate by reacting ethanol with ethanoic acid using concentrated sulfuric acid as a catalyst. The ester is then purified by removing impurities with sodium carbonate and calcium chloride solutions.
Equipment
- Thermometer
- Condenser
- 250 cm3 beaker
- Clamp and stand
- Bung
- Electric heater
- Dropping pipette
- Measuring cylinder
- Round bottomed flask with delivery arm
- Ethanoic acid
- Ethanol
- Concentrated sulfuric acid
- Sodium carbonate
- Calcium chloride solution
Method
- Attach the round-bottomed flask to a clamp stand. The condenser should be connected to the round-bottomed flask via a delivery tube.
- Place a beaker at the open end of the condenser.
- Add 10 cm3 ethanol, 12 cm3 ethanoic acid and 15 drops of concentrated sulfuric acid to the round-bottomed flask.
- Reconnect the round-bottomed flask to the apparatus and turn on the tap for the condenser.
- Gently heat the mixture using an electric heater. The ester will condense in the condenser before being collected in the beaker.
- Stop heating when no more ester is vapourising.
- Small quantities of sulfuric acid, ethanoic acid and ethanol may also be collected in the beaker. Add sodium carbonate to remove any acidic impurities. Stop adding sodium carbonate when the solution stops fizzing.
- Add calcium chloride solution to remove the ethanol.
Safety
- Be careful with fragile glassware.
- Concentrated sulfuric acid is very corrosive. Take care to avoid contact with the skin. Wash skin immediately if in contact with the acid.
- Ethanol and ethanoic acid are flammable so ensure there are no naked flames.
- Keep the laboratory well ventilated.
What are esters formed from?
A reaction between an alcohol and a carboxylic acid
A reaction between an acid and a salt
A reaction between an acid and a base
A reaction between a salt and a water
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What is the process of forming esters called?
Fermentation
Evaporation
Esterification
Distillation
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What is used as a catalyst in the process of esterification?
Sodium carbonate
Ethanoic acid
Concentrated sulfuric acid
Calcium chloride
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What is the purpose of adding sodium carbonate to the mixture in the beaker?
To increase the acidity of the mixture
To remove any acidic impurities
To cause a reaction with the ethanol
To create a base for the ester
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What is the purpose of adding calcium chloride solution to the mixture in the beaker?
To increase the acidity of the mixture
To create a base for the ester
To remove the ethanol
To cause a reaction with the ethanoic acid
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What safety measure should be taken when handling concentrated sulfuric acid?
Be careful with fragile glassware
Keep the laboratory well ventilated
Ensure there are no naked flames
Avoid contact with the skin and wash immediately if contact occurs
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What is the function of the condenser in the preparation of esters?
The condenser heats the mixture
The ester will condense in the condenser before being collected in the beaker
The condenser measures the amount of ester produced
The condenser adds concentrated sulfuric acid to the mixture
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What is the name of the process that forms esters?
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