| Date | May 2017 | Marks available | 1 | Reference code | 17M.3.sl.TZ1.14 |
| Level | SL | Paper | 3 | Time zone | TZ1 |
| Command term | Deduce | Question number | 14 | Adapted from | N/A |
Question
Carbon is produced by fusion reactions in stars.
The main fusion reaction responsible for the production of carbon is:
X + \(_2^4{\text{He}} \to _{\;6}^{12}{\text{C}}\)
Outline how the spectra of light from stars can be used to detect the presence of carbon.
Deduce the identity of X.
Outline why this reaction results in a release of energy.
Nuclear fusion reactors are predicted to become an important source of electrical energy in the future. State two advantages of nuclear fusion over nuclear fission.
Markscheme
presence of dark/absorption lines corresponding to those found for carbon
OR
missing wavelengths/frequencies correspond to carbon’s spectrum
Accept “presence of characteristic dark lines”.
Do not accept answer in terms of emission spectra.
[1 mark]
\({}_4^8Be\)
[1 mark]
product «nucleus» has a greater binding energy «per nucleon than reacting nuclei»
Accept “mass of the products is less than mass of the reactants”.
Accept converse arguments.
[1 mark]
fuel more abundant/cheaper
no «long half-life» radioisotopes/radioactive waste
shipment of radioactive fuels not required
plutonium/nuclear weapons cannot be produced from products
nuclear disasters less likely «as no critical mass of fuel required»
higher specific energy/energy per g/kg/unit mass than fission
Do not accept simply “fusion produces more energy than fission”.
[2 marks]
