Howlers of the week 2007
These are all genuine sentences and paragraphs that were written by students in their write-ups for the 2nd year practical on High Temperature Superconductivity, or library projects, or in exams. Remember that spelling mistakes, grammatical errors, and errors of logic are all entirely theirs, and have been reproduced exactly as they appeared on the student's script.
2nd year Theoretical Chemistry Exam question (2007):
Explain why the enthalpy of the following reaction is not zero:
3H218O + CaC16O3 = 3H216O + CaC18O3
- Energy is required to transfer the neutrons from the isotopes of oxygen.
- Due to the kinetic isotope effect, causes lighter isotope to be more favoured on specific compounds, as 18 electrons on oxygen means all full orbitals.
- 18O has two more electrons and has a higher bond order than 16O.
- The electron density in 18O is held more tightly to the nucleus than in 16O. So the reaction will energetically favour the reactants...
- There is a reaction going on in the oxygens. They are changing electronic states. So there is a transfer in electrons occuring.
- Because electron gain enthalpy can be positive or negative but 1st ionisation energy has to be negative.
- Because we are using radioactive oxygen which changes place during the reaction.
- Energy is required to transfer electrons from O to C in the forwards reaction and the opposite for the backwards reaction. Once carbon gets a full 3p6 shell it is very difficult to re-remove these electrons back to oxygen.
- The ionisation energy of ozone is greater to excite an electron than an oxygen atom. Therefore the enthalpy will not be in equilibrium during the reaction. The entropy will also be lower for the ozone atom because the excited state of an oxygen atom is more ordered.
[This is probably my favourite for thinking that CaCO3 contains ozone!].
- The isotopes of oxygen have changed in the two reagents during the reaction. The 18O which was in the H218O has returned to its ground state - releasing energy; whereas the CaC16O3 has been excited and moved to the second excited state. As not all of the energy released when the 18O drops to 16O can go into exiting the 16O to 18O (in CaCO3) then the enthalpy cannot have been zero.
- Because there is a constant flux between 16O to 18O states and 18C to 16C states.
- The radioactive isotope has higher energy and so they will be in different energy states and the size of the molecule may matter also.
- The energy required to break a 16O covalent bond is less than the energy required for a 18O bond due to the inert pair effect.
- Energy is needed to excited the oxygen atoms and energy is released when atoms drop down from their excited state BUT some energy is lost to the surroundings.
- 3 molecules of oxygen are being excited whereas only one molecule is returning to its ground state.
- The H216O formed is able to move faster to create more disorder.
2nd year Physical Chemistry Exam question (2007):
- The crystal is not a perect crystal and as such will have inferections. This inperections give rise to an entropy.
- Since T is constant, TdS = SdT
- Residual entropy is from errors in packing in the crystal, i.e. areas of extra muddling are frozen into the structure.
- As the CO cools so quickly, some of the CO forms a structure.
- A discrepency is frozen into the solid.
- Residual entropy is energy that has been encased in the solid at 0 K.
- Molar entropy of solid CO at 0 K is 5 J mol-1 K-1 due to residual entropy where by means when the process of cooling is fast some 'disorder' are trapped as causing the molar entropy at solid CO at 0 K is not zero.
- When the arrangement of the molecule is disorder, there is a possible that it may have an entropy.
- The Third law says that entropy is zero at 0K, if the crystal is perfick.
- The catalyst makes the reaction spontanus.
- The chemical potential is the amount of 'chemical punch' a molecule has.
3rd year Physical Chemistry Exam question (2007):
- Impurity atoms are added by dopping the Si substrate.
- To analyse a surface, use a photon gun to fire photons at a surface.
- All sites are eqaul in energy.
- The Langmuir isotherm assumes the surface is a homo genius.
- The atoms bond together to form a crystal lettuce.
- The molecules bounce across the surface and keep bouncing and bouncing until they find a place to rest. This bouncing mechanism works well.
- The metal surface is reduced by the addition of oxygen.
- Cu is extreamly hard to diposit on a divice.