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Date May 2017 Marks available 1 Reference code 17M.3.sl.TZ2.1
Level SL Paper 3 Time zone TZ2
Command term Estimate Question number 1 Adapted from N/A

Question

There is a link between world energy consumption and carbon dioxide production.

Climate induced changes in the ocean can be studied using measurements such as the Atmospheric Potential Oxygen (APO). Trends in APO concentration from two stations, one in each hemisphere, are shown below.

Trends in atmospheric potential oxygen (APO) based on monthly averages between 1990 and 2010.

[Source: www.ioos.noaa.gov]

The following graph represents world energy consumption by type for the years 1988–2013.

Estimate the percentage of energy consumption which did not directly produce CO2 in 2013.

[1]
a.

O2 is consumed in producing CO2 for electricity generation. The graph shows the relationship between the world’s electricity generation and CO2 production between 1994 and 2013.

Calculate the mass, in million tonnes, of oxygen gas ultimately found in CO2 which is consumed in generating 18 000 terawatts of electricity using the equation given for the best fit line. Give your answer to 2 significant figures.

Assume coal is the only energy source.

[2]
b.

The equilibrium expression for O2 exchange between the atmosphere and ocean is O2(g)  O2(aq). Identify one factor which shifts the equilibrium to the right.

[1]
c.i.

Factors such as photosynthesis and respiration are excluded so that APO is influenced by oceanic changes only. Suggest why the seasonal cycles from Alert station and Cape Grim observatory are different.

[2]
c.ii.

The change in APO O2/N2 ratio, per meg, is measured relative to an O2/N2 reference.

Δ ( O 2 / N 2 ) = ( ( O 2 / N 2 ) sample ( O 2 / N 2 ) reference 1 ) × 10 6

Calculate the APO Δ(O2/N2) value for an oxygen concentration of 209 400 ppm assuming that any change in N2 concentration is negligible. Reference values for O2 and N2 are 209 460 and 790 190 ppm respectively.

[1]
c.iii.

Suggest a reason for the general negative gradient of the APO curve given in (c).

[1]
c.iv.

Markscheme

« ( renewables + hydroelectricity + nuclear) total »

« ( 8800 7200 12600 ) × 100 = » 13 «%»

 

Accept range of “11–16%”.

[1 mark]

a.

«18000 = 0.54x – 2000»
x = 37037 «million tonnes of CO2»
« 32.00 44.01 x 37037 = 26930»
27000/2.7 x 104 «million tonnes of O2»

 

Accept “37000 «million tonnes of CO2»” for M1.

Award [2] for correct final answer with two significant figures.

Award [1] for non rounded answers in range 26903–26936 «million tonnes of O2».

[2 marks]

b.

increase in «atmospheric» pressure
OR
increase in [O2(g)]/concentration of O2(g)
OR
decrease in [O2(aq)]/concentration of O2(aq)
OR
decrease in temperature

 

Accept “increase in volume of oceans «due to polar ice cap melting»” OR “consumption of O2 in oceans/O2(aq)
«by living organisms»”.

State symbols required for oxygen concentration.

[1 mark]

c.i.

summer in one station while winter in other
OR
stations are at different latitudes

oxygen dissolves better in colder water

 

Accept “opposite seasons «in each hemisphere»”.

Do not accept “different locations with different temperatures” OR “stations are in different hemispheres”.

[2 marks]

c.ii.

« ( 209400 209460 1 ) × 10 6 =» − 286.5 «per meg»

 

The nitrogen cancels so is not needed in the calculation.

Negative sign required for mark.

[1 mark]

c.iii.

decrease in [O2]/concentration of O2
OR
increasing combustion of fossil fuels «consumes more O2 so [O2]/concentration of O2 decreases»
OR
warmer oceans/seas/water «as oxygen dissolves better in colder water»
OR
deforestation

 

Accept “decrease in level of O2”.

Accept "increasing CO2 production «consumes more O2 so [O2]/concentration of O2 decreases»".

Do not accept “decrease in amount of O2OR “increase in greenhouse gases”.

[1 mark]

c.iv.

Examiners report

[N/A]
a.
[N/A]
b.
[N/A]
c.i.
[N/A]
c.ii.
[N/A]
c.iii.
[N/A]
c.iv.

Syllabus sections

Core » Topic 11: Measurement and data processing » 11.2 Graphical techniques
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