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Option C: Energy
For HL students only
1a. [2 marks]
1.57 % of the mass of a rock weighing 46.5 kg is uranium(IV) oxide, UO2. 99.28 % of the uranium atoms in the rock are uranium-238, U238.
Show that the mass of the 238U isotope in the rock is 0.639 kg.
1b. [2 marks]
The half-life of 238U is 4.46×109 years. Calculate the mass of 238U that remains after 0.639 kg has decayed for 2.23×1010 years.
1c. [1 mark]
Outline a health risk produced by exposure to radioactive decay.
1d. [1 mark]
Deduce the nuclear equation for the decay of uranium-238 to thorium-234.
1e. [1 mark]
Thorium-234 has a higher binding energy per nucleon than uranium-238. Outline what is meant by the binding energy of a nucleus.
1f. [3 marks]
Determine the nuclear binding energy, in J, of U238 using sections 2 and 4 of the data booklet.
The mass of the U238 nucleus is 238.050786 amu.
2a. [3 marks]
Consider the following data for butane and pentane at STP.
Discuss the data.
2b. [1 mark]
Outline what is meant by the degradation of energy.
3a. [1 mark]
Red supergiant stars contain carbon-12 formed by the fusion of helium-4 nuclei with beryllium-8 nuclei.
Mass of a helium-4 nucleus = 4.002602 amu
Mass of a beryllium-8 nucleus = 8.005305 amu
Mass of a carbon-12 nucleus = 12.000000 amu
Mass of a beryllium-8 nucleus = 8.005305 amu
Mass of a carbon-12 nucleus = 12.000000 amu
State the nuclear equation for the fusion reaction.
3b. [2 marks]
Explain why fusion is an exothermic process.
3c. [3 marks]
Calculate the heat energy released, in J, by the fusion reaction producing one atom of carbon-12. Use section 2 of the data booklet and E = mc2.
3d. [2 marks]
Beryllium-8 is a radioactive isotope with a half-life of 6.70 × 10−17 s.
Calculate the mass of beryllium-8 remaining after 2.01 × 10−16 s from a sample initially containing 4.00 g of beryllium-8.
4a. [2 marks]
A proton-exchange membrane (PEM) fuel cell uses pure hydrogen gas as the fuel and a proton exchange membrane as the electrolyte.
Deduce the half-equations for the reactions occurring at the electrodes.
Anode (negative electrode):
Cathode (positive electrode):
4b. [1 mark]
Calculate the cell potential, Eθ, in V, using section 24 of the data booklet.
4c. [1 mark]
Suggest how PEM fuel cells can be used to produce a larger voltage than that calculated in (b)(i).
4d. [1 mark]
Suggest an advantage of the PEM fuel cell over the lead-acid battery for use in cars.
4e. [3 marks]
A dye-sensitized solar cell (DSSC) uses light energy to produce electricity.
Outline the functions of the dye, TiO2 and the electrolyte in the operation of the DSSC.
Dye:
TiO2:
Electrolyte:
4f. [1 mark]
Suggest an advantage of the DSSC over silicon-based photovoltaic cells.
5a. [1 mark]
Natural gas is an energy source composed mainly of methane.
Calculate the specific energy of methane, in MJ kg−1, using sections 1, 6 and 13 of the data booklet.
5b. [1 mark]
Natural gas is burned to produce steam which turns turbines in an electricity generating power plant.
The efficiency of several sources for power plants is given below.
Calculate the maximum electric energy output, in MJ, which can be obtained from burning 1.00 kg of methane by using your answer from (a).
5c. [2 marks]
Hydroelectric power plants produced 16% of the world’s energy in 2015, down from 21% in 1971.
Suggest why hydroelectric power production has a higher efficiency than the other sources given in (b) and why its relative use has decreased despite the high efficiency.
Reason for higher efficiency:
Reason for decreased use:
7d. [1 mark]
Methane can also be obtained by fractional distillation of crude oil.
If you need the markscheme, including the examiners' reports for each question, and more exam and teaching materials on this topic, contact me through the contact page