This question is about fuels - AQA - A-Level Chemistry - Question 2 - 2021 - Paper 2
Question 2
This question is about fuels.
The petrol fraction obtained from crude oil can be used as fuel in cars.
State the meaning of fraction, as used in the term petrol fr... show full transcript
Worked Solution & Example Answer:This question is about fuels - AQA - A-Level Chemistry - Question 2 - 2021 - Paper 2
Step 1
State the meaning of fraction, as used in the term petrol fraction.
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
In the context of fuels, a fraction refers to a specific range of hydrocarbons that have similar boiling points and can be separated during the refinement of crude oil.
Step 2
Complete the equation to show the cracking of one molecule of hexadecane to form hexane and cyclopentane only.
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
C₁₆H₃₄ → C₆H₁₄ + C₅H₁₂
Step 3
Give the name of a catalyst used in this cracking reaction.
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
A common catalyst used in cracking reactions is zeolite.
Step 4
Give a reason why carbon dioxide absorbs infrared radiation.
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
Carbon dioxide molecules possess vibrational modes that can absorb infrared radiation, which contributes to the greenhouse effect.
Step 5
Draw two curly arrows to complete the mechanism in Figure 1.
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
Curly arrows should be drawn from the lone pair on the nitrogen in Z to the carbon of CO₂, and from the C=O bond in CO₂ to the oxygen atom, indicating the formation of a bond and the breakdown of the double bond.
Step 6
Name compound Z (HOCH₂CH₂NH₂).
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
Compound Z is known as 2-aminoethanol (or ethylene glycol amine).
Step 7
Deduce the role of Z in step 2 of the mechanism.
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
In step 2 of the mechanism, Z acts as a base, accepting a proton to facilitate the reaction with carbon dioxide.
Step 8
Draw the shape of XNH₂.
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
The shape of XNH₂ (amine) is trigonal pyramidal due to the presence of a lone pair on nitrogen.
Step 9
[HOCH₂CH₂NH₂]⁻ can be represented as [XNH₃]. Explain your answer.
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
XNH₃ indicates a rigid tetrahedral shape with bond angles of approximately 107 degrees due to the lone pair-bond pair repulsion, being greater than the angles seen in a tetrahedral configuration.
Step 10
Bond angle
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
Approximately 107 degrees.
Step 11
Explanation
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 bond angle is affected by the presence of the lone pair on nitrogen, which pushes the H-N-H bond angles down from the ideal tetrahedral angle (109.5 degrees) to about 107 degrees.
Step 12
Evaluate the statement regarding bioethanol.
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
Bioethanol is produced through fermentation of sugars, typically from corn or sugarcane. When burned, it releases CO₂, which is nearly equal to the amount absorbed during its growth, positioning it as a carbon-neutral fuel. However, concerns arise about land use, production emissions, and its impact on food supply. Thus, while its carbon neutrality is a positive aspect, potential negative environmental impacts cannot be overlooked.
