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.
96%
114 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
The flask is not clamped, posing a risk of it falling and breaking.
The system is not sealed, which can lead to the escape of vapors and no control over pressure.
Step 2
Give one additional reagent that is needed to form any propanoic acid.
99%
104 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
Sulfuric acid needs to be added as a catalyst for the oxidation of propan-1-ol to form propanoic acid.
Step 3
State two more mistakes in the way the apparatus is set up in Figure 4.
96%
101 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
The direction of water flow through the condenser is incorrect; it should enter from the bottom.
A thermometer is not needed in this setup as it does not measure the necessary temperature accurately.
Step 4
State the purpose of the small glass beads in the flask in Figure 4.
98%
120 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
The small glass beads are used to prevent 'bumping' by providing a surface for the liquid to boil smoothly.
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. The propanoic acid separated from the reaction mixture has a mass of 3.25 g. State the name of the technique used to separate the propanoic acid from the reaction mixture. Calculate the percentage yield of propanoic acid.
97%
117 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
The technique used to separate propanoic acid is fractional distillation.
To calculate the percentage yield of propanoic acid, use the formula:
State a simple chemical test that distinguishes the propanoic acid from the propan-1-ol. Give one observation for the test with each substance.
97%
121 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
Test: Add sodium carbonate.
Observation: For propanoic acid, effervescence of bubbles will occur due to the release of carbon dioxide. For propan-1-ol, no visible reaction will occur.
