Date | November 2020 | Marks available | 2 | Reference code | 20N.2.SL.TZ0.6 |
Level | Standard level | Paper | Paper 2 | Time zone | 0 - no time zone |
Command term | Calculate | Question number | 6 | Adapted from | N/A |
Question
One possible fission reaction of uranium-235 (U-235) is
Mass of one atom of U-235
Binding energy per nucleon for U-235
Binding energy per nucleon for Xe-140
Binding energy per nucleon for Sr-94
A nuclear power station uses U-235 as fuel. Assume that every fission reaction of U-235 gives rise to of energy.
A sample of waste produced by the reactor contains of strontium-94 (Sr-94). Sr-94 is radioactive and undergoes beta-minus () decay into a daughter nuclide X. The reaction for this decay is
.
The graph shows the variation with time of the mass of Sr-94 remaining in the sample.
State what is meant by binding energy of a nucleus.
Outline why quantities such as atomic mass and nuclear binding energy are often expressed in non-SI units.
Show that the energy released in the reaction is about .
Estimate, in , the specific energy of U-235.
The power station has a useful power output of and an efficiency of . Determine the mass of U-235 that undergoes fission in one day.
Write down the proton number of nuclide X.
State the half-life of Sr-94.
Calculate the mass of Sr-94 remaining in the sample after minutes.
Markscheme
energy required to «completely» separate the nucleons
OR
energy released when a nucleus is formed from its constituent nucleons ✓
Allow protons AND neutrons.
the values «in SI units» would be very small ✓
OR ✓
see AND ✓
✓
energy produced in one day ✓
mass ✓
✓
Do not allow unless the proton number is indicated.
✓
ALTERNATIVE 1
✓
mass remaining ✓
ALTERNATIVE 2
decay constant ✓
mass remaining ✓