A student plans an experiment to investigate the yield of propanoic acid when a sample of propan-1-ol is oxidised - AQA - A-Level Chemistry - Question 6 - 2021 - Paper 3

Sulfuric acid (or phosphoric acid) is needed as a catalyst in the oxidation of propan-1-ol.

1. The direction of water flow through the condenser is incorrect and should be from the bottom to the top.
2. The thermometer is not necessary for measuring the temperature of the reaction in this setup.

The small glass beads are used to provide a larger surface area for the reaction and to prevent bumping during boiling.

Fractional distillation.

To find the percentage yield:

1. Calculate the theoretical yield of propanoic acid from 6.50 g of propan-1-ol:

   Molar mass of propan-1-ol = 60.10 g/mol Moles of propan-1-ol = \frac{6.50 \text{ g}}{60.10 \text{ g/mol}} \approx 0.108 \text{ mol}

   Based on the reaction stoichiometry: \text{1 mol propan-1-ol produces 1 mol propanoic acid}

   Theoretical yield of propanoic acid: \text{Mass} = 0.108 \text{ mol} \times 74.08 , \text{g/mol} \approx 8.00 , \text{g}.

2. Actual yield is 3.25 g.

3. Percentage yield = \frac{\text{actual yield}}{\text{theoretical yield}} \times 100 = \frac{3.25}{8.00} \times 100 \approx 40.625%.

Add sodium carbonate to the samples. Propanoic acid will react with sodium carbonate to produce carbon dioxide gas, while propan-1-ol will not.

Give one observation for the test with each substance:

1. Propanoic acid: Effervescence, bubbles are observed.
2. Propan-1-ol: No visible change or reaction.