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Date November 2016 Marks available 2 Reference code 16N.2.SL.TZ0.8
Level Standard level Paper Paper 2 Time zone Time zone 0
Command term Explain Question number 8 Adapted from N/A

Question

The following data are available for a natural gas power station that has a high efficiency.

Rate of consumption of natural gas = 14.6 kg s–1
Specific energy of natural gas = 55.5 MJ kg–1
Efficiency of electrical power generation = 59.0 %
Mass of CO2 generated per kg of natural gas = 2.75 kg
One year = 3.16 × 107

Calculate, with a suitable unit, the electrical power output of the power station.

[1]
a.

Calculate the mass of CO2 generated in a year assuming the power station operates continuously.

[1]
b.

Explain, using your answer to (b), why countries are being asked to decrease their dependence on fossil fuels.

[2]
c.

Describe, in terms of energy transfers, how thermal energy of the burning gas becomes electrical energy.

[2]
d.

Markscheme

«55.5 × 14.6 × 0.59» 4.78 × 108 W

A unit is required for this mark. Allow use of J s1.

No sf penalty.

a.

«14.6 × 2.75 × 3.16 × 107 =» 1.27 × 109 «kg»

If no unit assume kg

b.

CO2 linked to greenhouse gas OR greenhouse effect

leading to «enhanced» global warming
OR
climate change
OR
other reasonable climatic effect

c.

Internal energy of steam/particles OR KE of steam/particles

«transfers to» KE of turbine

«transfers to» KE of generator or dynamo «producing electrical energy»

Do not award mark for first and last energies as they are given in the question.

Do not allow “gas” for “steam”

Do not accept reference to moving OR turning generator

d.

Examiners report

[N/A]
a.
[N/A]
b.
[N/A]
c.
[N/A]
d.

Syllabus sections

Core » Topic 8: Energy production » 8.1 – Energy sources
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