Question 1: Define an ester in terms of its chemical structure.

Answer: An ester is an organic compound derived from a carboxylic acid and an alcohol, characterised by the functional group -COO-.

Question 2: Describe the general method for synthesising esters in the laboratory.

Answer: Esters are synthesised through a reaction called esterification, where a carboxylic acid reacts with an alcohol in the presence of a catalyst, usually sulphuric acid.

Question 3: Explain why esters often have distinctive smells and give an example.

Answer: Esters have distinctive smells because their molecular structures interact with olfactory receptors; for example, ethyl acetate smells like nail polish remover.

Question 1: Calculate the molar mass of ethyl ethanoate (ethyl acetate). (C4H8O2)

Answer: 88 g/mol

Question 2: If 10 grams of ethanoic acid reacts completely with excess ethanol, how many moles of ester can be produced? (Molar mass of ethanoic acid = 60 g/mol)

Answer: 0.167 moles

Question 1: Describe the key safety precautions that should be taken when synthesising esters in the laboratory.

Answer: Use protective gloves and goggles, work in a well-ventilated area or fume cupboard, and handle acids and alcohols with care to avoid burns or inhalation.

Question 2: Identify the variables that need to be controlled during an ester synthesis experiment.

Answer: Temperature, concentration of reactants, reaction time, and catalyst presence.

Question 1: A student performs an esterification reaction and notes a sweet smell. Explain why esters often have pleasant odours and how this relates to their molecular structure.

Answer: Esters often have pleasant odours because their molecular structures can interact with olfactory receptors, mimicking fruity or floral scents. The functional group -COO- and the alkyl groups attached influence the scent profile, making esters useful in flavourings and perfumes.

Question 1: Describe the industrial process used to produce ethyl acetate on a large scale, including raw materials and conditions.

Answer: In industry, ethyl acetate is produced by the esterification of ethanoic acid with ethanol, often in the presence of a catalyst such as sulphuric acid under reflux conditions. Excess reactant and continuous removal of water help drive the reaction to completion, enabling large-scale production.

Question 2: Explain how the properties of esters make them suitable for use in perfumes and artificial flavours.

Answer: Esters have pleasant, distinctive smells that resemble fruits and flowers, making them ideal for perfumes and artificial flavours. Their volatility and ability to interact with olfactory receptors enhance their effectiveness in these applications.