Question 1: Esters are organic compounds derived from carboxylic acids and alcohols. They are characterised by a distinctive sweet aroma and are commonly used in fragrances and flavourings. The general structure of an ester is R–CO–O–R'.

Answer: Esters are organic compounds with the structure R–CO–O–R', formed from carboxylic acids and alcohols.

Question 1: Describe the process of esterification and name the catalyst commonly used.

Answer: Esterification is a reaction between a carboxylic acid and an alcohol, producing an ester and water, usually catalysed by concentrated sulphuric acid.

Question 2: Identify the reactants and products in the esterification of ethanoic acid with ethanol.

Answer: Reactants: ethanoic acid and ethanol; Products: ethyl ethanoate (an ester) and water.

Question 1: Outline a basic experimental procedure for synthesising an ester in the laboratory, including safety precautions.

Answer: To synthesise an ester, mix a carboxylic acid with an alcohol in a flask, add a few drops of concentrated sulphuric acid as a catalyst, then gently heat under reflux. Safety precautions include wearing safety goggles, gloves, and working in a well-ventilated fume cupboard to handle acids and volatile solvents.

Question 1: A student prepared an ester by reacting ethanoic acid with ethanol. The resulting ester has a sweet smell. Explain why esters are often associated with pleasant odours and give two examples of their uses in industry.

Answer: Esters have distinctive sweet or fruity odours due to their molecular structure, which interacts with olfactory receptors. They are used in fragrances (e.g., methyl butanoate in fruit scents) and as flavourings in food products (e.g., vanillin esters).

Question 1: Explain how esters are used in the production of artificial flavours and fragrances, and discuss any safety considerations involved.

Answer: Esters are synthesised to mimic natural fruit and floral scents used in perfumes and flavourings. Safety considerations include ensuring proper handling of volatile chemicals, avoiding inhalation or skin contact, and using appropriate ventilation and protective equipment.

Question 2: Calculate the volume of ethanol (density 0.789 g/cm³) required to produce 50g of a specific ester, assuming the molar ratio is 1:1 and the molar mass of ethanol is 46 g/mol.

Answer: Number of moles of ester = mass / molar mass; volume of ethanol = moles × molar volume (22.4 L/mol) / density. Calculation steps provided in the student's answer.

Question 1: Summarise the key points about the formation, properties, and uses of esters.

Answer: Esters are formed from acids and alcohols via esterification, have sweet smells, and are used in fragrances, flavourings, and industry for their pleasant odours and applications.