a) Diagram A shows an arrangement used to reflux the reaction mixture in an experiment to prepare a sample of soap - Leaving Cert Chemistry - Question 2 - 2018

The purpose of refluxing a reaction mixture is to heat the reaction mixture without losing volatile components. This ensures that the reactants are kept at a constant temperature and allows the reaction to proceed to completion by providing energy to overcome the activation energy.

The two reactants are sodium hydroxide (NaOH) and fats or fatty acids. The solvent initially present in the flask is typically water.

An emulsion is a mixture of two immiscible liquids, where one liquid is dispersed in the other in the form of small droplets. In this case, the emulsion consists of oil droplets in water, where oil is insoluble in water.

A suitable organic solvent for the extraction of clove oil is dichloromethane (CH₂Cl₂) or ethyl acetate.

One safety precaution is to keep the stopper in place while shaking the separating funnel to avoid any leakage or pressure build-up.

The clove oil is isolated by allowing the separating funnel to settle, then carefully draining the lower aqueous layer. The remaining organic layer containing the clove oil is collected.

To find the percentage yield, first calculate the mass of clove oil obtained using the formula:

$\text{mass} = \text{volume} \times \text{density}$

So, for 0.15 cm³ of clove oil with a density of 1.05 g cm⁻³, the mass is:

$m = 0.15 \text{ cm}^3 \times 1.05 \text{ g cm}^{-3} = 0.1575 \text{ g}$

Next, calculate the percentage yield using the formula:

$\text{Percentage Yield} = \left( \frac{\text{mass of clove oil}}{\text{mass of cloves used}} \right) \times 100$

Substituting the values:

$\text{Percentage Yield} = \left( \frac{0.1575}{5.0} \right) \times 100 = 3.15\%$

Thus, the percentage yield of clove oil is approximately 3.15%.

There is no need for additional purification steps following recrystallisation because the process itself effectively removes impurities, allowing for the collection of pure, recrystallised benzoic acid.

One advantage of suction filtration is that it allows for the rapid separation of solid crystals from a liquid, thus saving time in the purification process.

You could verify the purity of the recrystallised benzoic acid by measuring and comparing the melting points of both the original and recrystallised samples. The recrystallised sample should exhibit a higher melting point and a sharper melting point range, indicating greater purity.