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) might be expected but some are surprising since the chemistry can seem quite straightforward (e.g. the difference between intra- and inter-molecular forces of attraction). Listed below is my own list.  On separate pages I have explained for most of them exactly what the problem seems to be. 

By being aware of these problem areas and by addressing them beforehand you can hopefully improve your performance in the examinations.

My top ten areas (in no particular order)

  1. Standard Level Higher Level Understanding the activity series 

  2. Standard Level Higher Level  VSEPR (Shapes of simple molecules and ions)

  3. Standard Level Higher Level  Explaining the shapes of IE graph(s)  

  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  Understanding and using ΔG  

  8. Higher Level  Factors affecting the rate of nucleophilic substitution reactions

  9. Higher Level  Using electrode potentials  

10. Higher Level  Understanding hybridization  

One other area where some students surprisingly have difficulty is confusing intramolecular and intermolecular forces. Make sure you understand that the reason ethanol, C2H5OH, has a higher boiling point than its structural isomer methoxymethane, CH3OCH3, is because ethanol molecules, unlike methoxymethane molecules, hydrogen bond to each other - it is not because breaking the O-H bond requires more energy!!

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