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
Question 6
A student plans an experiment to investigate the yield of propanoic acid when a sample of propan-1-ol is oxidised.
Figure 4 shows the apparatus that the student pla... show full transcript
Worked Solution & Example Answer: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
Step 1
Give two reasons why the apparatus shown in Figure 4 is not safe.
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Answer
The flask is not clamped, which can lead to it tipping over and causing spills.
The system is not sealed properly, which can allow harmful vapors to escape.
Step 2
Give one additional reagent that is needed to form any propanoic acid.
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Answer
Sulfuric acid is needed as a catalyst for the oxidation process.
Step 3
State two more mistakes in the way the apparatus is set up in Figure 4.
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The direction of water flow through the condenser should be from the bottom to the top to maintain efficient cooling.
The thermometer is not needed and creates additional safety risks in this setup.
Step 4
State the purpose of the small glass beads in the flask in Figure 4.
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The small glass beads are used to promote even heating and prevent 'bumping' during the reaction.
Step 5
After correcting the mistakes, the student heats a reaction mixture containing 6.50 g of propan-1-ol with an excess of the oxidising agent...
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Answer
The technique used to separate the propanoic acid is fractional distillation.
To calculate the percentage yield:
Calculate the moles of propan-1-ol:
Molar mass of propan-1-ol = 60.1 g/mol
Moles of propan-1-ol = ( \frac{6.50 , ext{g}}{60.1 , ext{g/mol}} \approx 0.108 , ext{mol} )
Calculate theoretical yield of propanoic acid = 0.108 mol × 74.1 g/mol = 8.00 g (theoretical maximum).
