Question 1: Define a carboxylic acid and describe its functional group.

Answer: A carboxylic acid is an organic compound containing a carboxyl functional group (-COOH).

Question 2: Explain the mechanism by which carboxylic acids react with sodium metal.

Answer: Carboxylic acids react with sodium metal via acid-base reaction, producing a salt (sodium carboxylate) and hydrogen gas.

Question 3: Write the general formula for a carboxylic acid.

Answer: R-COOH, where R represents a hydrocarbon chain.

Question 1: Calculate the number of moles in 25 cm³ of a 0.1 mol/dm³ acetic acid solution. (Use 1000 cm³ = 1 dm³)

Answer: 0.0025 mol

Question 2: If 50 cm³ of sodium hydroxide solution reacts completely with 20 cm³ of a carboxylic acid, and the concentration of NaOH is 0.2 mol/dm³, what is the concentration of the acid?

Answer: 0.04 mol/dm³

Question 1: Describe a safe method to prepare a dilute solution of ethanoic acid in the laboratory. Include safety precautions.

Answer: To prepare a dilute solution of ethanoic acid, carefully measure a small volume of concentrated acid using a measuring cylinder and add it slowly to a known volume of distilled water while stirring. Wear safety goggles and gloves, and add acid to water, not water to acid to prevent splashing.

Question 2: Identify the independent, dependent, and control variables in an experiment to test the reactivity of carboxylic acids with metals.

Answer: Independent variable: Type of metal used; Dependent variable: Rate of hydrogen gas production; Control variables: Concentration of acid, temperature, and acid volume.

Question 1: A sample of a carboxylic acid has a pH of 2.5. Explain what this indicates about its acidity compared to a solution with pH 7.

Answer: A pH of 2.5 indicates the solution is acidic, with a high concentration of hydrogen ions, much more acidic than neutral pH 7.

Question 2: A student measures the volume of a carboxylic acid required to neutralise a known concentration of sodium carbonate. The data shows 25 cm³ of acid reacts with 20 cm³ of sodium carbonate solution at 0.1 mol/dm³. Describe how to determine the molarity of the acid.

Answer: Calculate the moles of sodium carbonate reacting using its concentration and volume. Use the balanced equation to find the molar ratio between acid and carbonate. Then, divide the moles of acid by its volume to find its molarity.

Question 1: Explain how carboxylic acids are used in the food industry, providing a specific example.

Answer: Carboxylic acids like citric acid are used as preservatives and flavouring agents in food and beverages, for example, in soft drinks to add tartness.

Question 2: Describe how carboxylic acids are involved in the manufacturing of soaps and detergents.

Answer: Carboxylic acids, specifically fatty acids, are used to produce soap through the process of saponification, where they react with alkali to form soap molecules.