DP Chemistry (last assessment 2024)

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Question 23M.3.SL.TZ2.12

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Date May 2023 Marks available [Maximum mark: 8] Reference code 23M.3.SL.TZ2.12
Level SL Paper 3 Time zone TZ2
Command term Determine, Distinguish, Outline, State, Suggest Question number 12 Adapted from N/A
12.
[Maximum mark: 8]
23M.3.SL.TZ2.12

Geological transformations produce fossil fuels.

(a)

Combustion of coal emits particulates into the atmosphere.

(a.i)

Outline why this affects global warming.

[1]

Markscheme

reflects «sun» light ✓

 

Accept “results in global dimming”
OR
“reduces the amount of energy reaching the Earth”
OR
“acts as nucleation points for cloud formation”.

Do not accept answers that only indicate increases in global temperatures.

(a.ii)

State the major form of energy produced by the combustion of coal.

[1]

Markscheme

electrical/electricity ✓

 

Accept “heat/thermal”.

(b)

Conversion of petroleum to petrol (gasoline) involves fractional distillation and cracking.

Distinguish between these processes.

 

Fractional distillation: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

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Cracking: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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[2]

Markscheme

Fractional distillation (Any one of):
separates compounds according to boiling points/vapor pressure
OR
physical process
OR
involves breaking intermolecular forces
OR
separates based on molar masses
OR
does not use catalyst ✓

Cracking (Any one of):
shorter hydrocarbon chains formed/lower molar masses
OR
increased branching formed
OR
increased aromatic ring formation
OR
produces alkenes/unsaturated hydrocarbons
OR
chemical process
OR
new compounds formed/breaking «and remaking»/changing covalent bonds
OR
uses catalyst ✓

 

M1 is for Fractional distillation.

M2 is for Cracking.

(c)

The equation for the combustion of octane is:

C8H18 (l) + 1212O2 → 8CO2 (g) + 9H2O (l)

(c.i)

Determine the mass of carbon dioxide, in g, produced when 1 kJ of energy is produced. Use section 13 of the data booklet.

[3]

Markscheme

ALTERNATIVE 1
5470 «kJ» produced when 8 «mol» produced ✓

«8 × 44.01 =» 352 «g» to produce 5470 «kJ» ✓

1 «kJ» would release «352/5470 =» 0.0644 «g» ✓

ALTERNATIVE 2
1 «kJ»/5470«kJ=» 1.828x10−4 ✓

8/5470 «mol =» 0.001463 mol ✓

«8/5470 «mol» × 44.01 «gmol−1 =» 0.0644 «g» ✓

 

Award [3] for correct final answer.

Accept "0.0643 «g»".

(c.ii)

Suggest a piece of evidence that leads some people to not accept a causal link between the industrial emission of greenhouse gases, such as CO2, and global warming.

[1]

Markscheme

many fluctuations of temperature have occurred in the «geological» past
OR
different global models produce different outcomes
OR
industrial emissions are less than natural ones ✓

 

Do not accept statements about current temperatures.