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This question is about esters including biodiesel - AQA - A-Level Chemistry - Question 11 - 2019 - Paper 2
Question 11
This question is about esters including biodiesel. An ester is formed by the reaction of an acid anhydride with CH₃CH₂OH. Complete the equation. In your answer show... show full transcript
Worked Solution & Example Answer:This question is about esters including biodiesel - AQA - A-Level Chemistry - Question 11 - 2019 - Paper 2
Step 1
Step 2
Draw the structure of the vegetable oil showing clearly the ester links.
Answer
The structure of the vegetable oil with the ester links can be represented as follows:
R₁ R₂
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C₁ -- C₁ -- C₁ -- O -- C -- C
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H x C H x C
Where R₁ and R₂ represent the hydrocarbon chains, each connected to the ester functional group.
Step 3
Complete the skeletal formula to show the next part of the hydrocarbon chain to carbon atom number 14. In your answer, show the Z stereochemistry around both C=C double bonds.
Answer
The skeletal formula extending to carbon number 14 with indicated Z stereochemistry is shown as:
HOOC - CH = CH (Z) - CH₂ - CH = CH (Z) - C - CH₂ - CH₃
This shows the correct formatting for the double bonds as per the Z configuration.
Step 4
Step 5
State how the infrared spectrum of carbon dioxide in Figure 3 is not what you might predict from the data provided in Table A in the Data Booklet.
Answer
The infrared spectrum of carbon dioxide in Figure 3 shows strong absorbance peaks at specific wavenumbers, which do not align with the simple predictions based on molecular vibrations as detailed in Table A. Specifically, data suggests characteristic absorbance in different regions than observed.
Step 6
Explain how carbon dioxide causes global warming.
Answer
Carbon dioxide contributes to global warming through its greenhouse effect. It absorbs infrared radiation emitted by the Earth's surface and re-emits it in all directions, thereby trapping heat within the atmosphere. This process leads to a rise in global temperatures.