Areas of difficulty

Areas where students experience difficulties on Paper 2 

I’ve been marking IB Chemistry papers now for a long time and there are several areas that every year many students seem to find particularly difficult. Some of these (such as hybridization) we might expect but some may be surprising to us as teachers since the chemistry can seem quite straightforward (e.g. the difference between intra- and inter-molecular forces of attraction). Listed below is my own top ten list.  On separate pages I have explained for each one what the problem seems to be.  You can widen this and see other examples by looking at the Chief Examiner reports which are published after every session. These can be downloaded from the programme resources section of My IB.

By being aware of these problem areas and by addressing them beforehand we can hopefully improve our own students’ performance in the examinations.

My top ten areas (in no particular order)

  1. Standard Level Higher Level Intermolecular forces of attraction

  2. Standard Level Higher Level Shapes of simple molecules and ions

  3. Standard Level Higher Level Explaining the shape of IE graph

  4. Standard Level Higher Level Misuse of formulas in stoichiometric relationships

  5. Standard Level Higher Level  Manipulating equilibrium constants

  6. Higher Level ‘Curly arrows'

  7. Higher Level  ΔG calculations 

  8. Higher Level Calculation of Kc values 

  9. Higher Level Oxidant and reductant from EStandard Sign values

10. Higher Level  Understanding hybridization

In addition I have also included a page on Standard Level Higher Level  Understanding the activity series as it can be confusing to students to see lithium above potassium in the activity series given in Section 25 of the IB data booklet when they know that potassium reacts more vigorously than lithium when the metals are added to water. One other area where students (and sometimes teachers too) have difficulty is how the choice of solvent affects the rate of SN1 and SN2 reactions as the IB guide has caused some problems so I have also included a page on Higher Level Factors affecting the rate of nucleophilic substitution reactions.

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