Hi, how is this paper compared to precious years? some say is
manageable but some also say harder than prelims
1. For the question on hydrogen and methanol fuel cell, why is
there no value for combustion of petrol? Can I write cos combustion
of petrol cannot be done under standard conditions?
2. For FRS question, why is there increasing rate of reaction
after bright light removed? Can I say radicals are very reactive
and the subsequent termination steps are faster cos it only involve
radicals?
3. Why is there a reaction only after there's bright light? Isit
cos to lower activation energy?
4. I carelessly drew sn1 instead of sn2. Is that zero marks?
5.For planning, I only write out the steps and no calculations
and explanations on how to find the concentrations, how many marks
is that?
Q1. Petrol is a mixture of alkanes, cycloalkanes, and alkenes, with
between 4 and 12 carbon atoms per molecule. Hence it doesn't have a
fixed combustion enthalpy value.
Q2. Due to the large no. of different possible propagation
reactions, free-radical concentrations will continue to increase,
hence increasing rate of reaction, until the rate of termination
reactions catch up.
Q3. To *provide* the activation energy, not lower it.
Q4. Yes, zero marks.
Q5. Depends on exactly what you wrote. It's impossible to determine
exactly how many marks you can get from Planning, and you shouldn't
bother so much with it. Just do your best with the remaining
Papers, and if you do well enough for them (since the overall score
is an aggregate of all papers), you can still get your A grade.