| Date | May 2018 | Marks available | 2 | Reference code | 18M.3.hl.TZ2.16 |
| Level | HL | Paper | 3 | Time zone | TZ2 |
| Command term | Calculate | Question number | 16 | Adapted from | N/A |
Question
Nuclear power is another source of energy.
235U atoms can be used in nuclear reactors whereas 238U cannot. A centrifuge is used to separate isotopes.
Calculate the relative rate of effusion of 235UF6(g) to 238UF6(g) using sections 1 and 6 of the data booklet.
Explain, based on molecular structure and bonding, why diffusion or centrifuging can be used for enrichment of UF6 but not UO2.
Markscheme
Mr(235UF6) = 235 + (19.00 × 6)/349
OR
Mr(238UF6) = 238 + (19.00 × 6)/352
«» 1.004
Award [2] for correct final answer.
Do not accept “1.00” OR “0.996”.
[2 marks]
UF6: Structure: octahedral «solid»/square bipyramidal «solid»/«simple» molecular solid/simple molecule AND Bonding: covalent
UO2: Structure: crystal/lattice/network «solid»/«resembles» fluorite AND Bonding: «partly» covalent
UF6 sublimes/evaporates/boils at low temperature
Accept “UF6: Structure: octahedral «solid»/square bipyramidal «solid»/«simple» molecular solid/simple molecule AND weak intermolecular/London/dispersion/van der Waals’/vdW forces”.
Accept “non-polar molecule” for “«simple» molecular solid”.
Accept “giant molecular” OR “macromolecular” for “network”.
Accept “ionic/electrostatic attractions «between ions»” for bonding in UO2.
Award M2 for “UO2: network covalent/covalent network/giant covalent” OR “UO2: network ionic/giant ionic”.
For M1 and M2 award [1 max] for two correct structures OR two bonding types.
Accept any specified low temperature in the range 56–65 °C.
Examiners report
Syllabus sections
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17N.3.hl.TZ0.18c.i:
Calculate the loss in mass, in kg, and the energy released, in J, when 0.00100 mol of 228Ac decays, each atom losing an electron. Use section 2 of the data booklet and E = mc2.
228Ac → + 228Th
- 18N.3.hl.TZ0.12d.ii: Explain why free radicals are harmful to living cells.
-
18N.3.hl.TZ0.12d.i:
Deduce a Lewis (electron dot) structure of the superoxide, O2–, free radical.
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17N.3.hl.TZ0.18c.ii:
Determine the energy released, in J, by 0.00100 mol of 228Ac over the course of 18 hours.
- 17N.3.hl.TZ0.18d: Outline how nuclear ionising radiation can damage DNA and enzymes in living cells.
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18M.3.hl.TZ2.16c.ii:
Explain, based on molecular structure and bonding, why diffusion or centrifuging can be used for enrichment of UF6 but not UO2.
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19M.3.hl.TZ2.16c:
Outline how the energy of a fission reaction can be calculated.
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18M.3.hl.TZ1.14b.ii:
Explain how the proportion of 235U in natural uranium is increased.
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17M.3.hl.TZ1.18b.ii:
The mass of X is 8.005305 amu and that of is 4.002603 amu. Determine the energy produced, in J, when one atom of is formed in this reaction. Use section 2 of the data booklet.
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19M.3.hl.TZ1.16c:
The daughter product, 89Kr, has a half-life of 3.15 min.
Calculate the time required, in minutes, for its radioactivity to fall to 10% of its initial value, using section 1 of the data booklet.
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19M.3.hl.TZ2.16d:
Calculate the half-life of an isotope whose mass falls from 5.0 × 10−5 g to 4.0 × 10−5 g in 31.4 s, using section 1 of the data booklet.
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17M.3.hl.TZ2.16a.iii:
Calculate the energy released, in MeV, in this reaction, using section 36 of the data booklet.
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19N.3.hl.TZ0.18a(iii):
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.
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20N.3.hl.TZ0.11e(iv):
Determine the relative rate of effusion of methane () to carbon dioxide (), under the same conditions of temperature and pressure. Use section 1 of the data booklet.
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20N.3.hl.TZ0.12f:
Determine the nuclear binding energy, in , of using sections 2 and 4 of the data booklet.
The mass of the nucleus is .
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19M.3.hl.TZ1.16a(iii):
The masses of the particles involved in this fission reaction are shown below.
Mass of neutron = 1.00867 amu
Mass of U-235 nucleus = 234.99346 amu
Mass of Ba-144 nucleus = 143.89223 amu
Mass of Kr-89 nucleus = 88.89788 amuDetermine the energy released, in J, when one uranium-235 nucleus undergoes fission. Use this data and information from sections 1 and 2 of the data booklet.
