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This question is about ethanoic acid (HOOCCH3) and the ethanoate ion (COO") - AQA - A-Level Chemistry - Question 1 - 2021 - Paper 3
Question 1
This question is about ethanoic acid (HOOCCH3) and the ethanoate ion (COO"). Ethanoic acid reacts with propane-1,3-diol (HOCH2CH(CH3)OH) to form a polyester. Draw ... show full transcript
Worked Solution & Example Answer:This question is about ethanoic acid (HOOCCH3) and the ethanoate ion (COO") - AQA - A-Level Chemistry - Question 1 - 2021 - Paper 3
Step 1
Draw the repeating unit of this polyester.
Answer
The repeating unit of the polyester formed from ethanoic acid and propane-1,3-diol includes the ester link and the carbon chain structure. It can be represented as follows:
O
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–C–C–C–
| |
H H
The molecular structure involves a chain of carbon atoms with ester linkages forming between the acids and alcohol.
Step 2
Explain why polyesters are biodegradable but polyalkenes are not biodegradable.
Answer
Polyesters are biodegradable because they can be broken down by microorganisms into natural substances. They possess polar functional groups that facilitate this process, making it easier for bacteria and fungi to metabolize them.
In contrast, polyalkenes lack polar functional groups; they are non-polar and stable chemical structures that resist microbial attack. Thus, polyalkenes remain in the environment for a longer duration, contributing to pollution.
Step 3
Calculate the concentration, in mol dm⁻³, of the potassium manganate(VII) solution.
Answer
To find the concentration of potassium manganate(VII), we first need to determine the number of moles of sodium oxalate:
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Calculate the moles of Na2C2O4:
Moles =
\frac{mass}{Mr} = \frac{162 g}{134.0 g/mol} = 1.21 molFor 250 cm³ (0.250 dm³):
ext{Concentration} = \frac{1.21 mol}{0.250 dm³} = 4.84 mol/dm³
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Since 5 moles of C2O4^{2-} react with 2 moles of MnO4^-:
\frac{2}{5} \times Moles = \frac{2}{5} \times 1.21 mol = 0.484 mol
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For the titration volume of 0.02385 dm³:
ext{Concentration of MnO4^-} = \frac{0.484 mol}{0.02385 dm³} = 20.25 mol/dm³
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Step 4
Suggest safety precautions, other than eye protection, that should be taken when filling the burette with potassium manganate(VII) solution.
Answer
- Ensure that the burette is closed at the base to avoid spills and leaks.
- Use gloves to avoid skin contact, and work in a well-ventilated area to prevent inhalation of vapors.
Step 5
Suggest safety precautions, other than eye protection, that should be taken when dissolving the solid sodium ethanoate in water.
Answer
- Always add solid sodium ethanoate to water slowly to minimize splashing and ensure safe mixing.
- Use a spatula and lab coat to protect against spills and contact with the solid.
Step 6
Step 7