Although some multiple choice questions can be quite challenging generally the markscheme is clear and there is only one correct answer for each question. In fact as you can see (below) from the instructions given on the front of the question paper students are required to give the best answer rather than the correct answer as occasionally another answer apart from the best answer could be considered correct under certain specific circumstances.

But what happens if there is more than one ‘best’ answer? Teachers are encouraged to do the paper themselves after the students have sat the examination and comment on the G2 form about any particular problems they have come across. At the grade award meeting these comments are scrutinized and if the examiners agree they have the option to delete the question or allow two right answers. An example of this occurred in the M2001 Paper 1 SL examination. Question 11 asked which out of MgS, HCl, CO₂ and CaO had the greatest ionic character. Initially the answer given was CaO as it has the largest difference in electronegativity values. However some teachers argued that the states were not given and HCl is a strong acid in aqueous solution so is fully dissociated into ions. At the grade award meeting it was decided to accept both HCl and CaO as correct answers. When this does happen the decision is referred to in the Chief Examiner’s Report published shortly after the examination session has ended.

Within the next few weeks teachers are likely to be giving a mock examination to their students and one of the likely contenders for the mock exam are the May 2010 TZ1 papers. Take a look at Question 22 on the SL Paper 1 (the same question appears as Question 26 on the corresponding Higher Level Paper). Essentially the question asks which is the correct statement about two solutions of equal volumes of NaOH(aq) and NH₃(aq) when both solutions have a concentration of  1.0 mol dm^-3. The answer according to the markscheme is answer C which states that sodium hydroxide has a higher pH than ammonia. This is clearly correct and the two answers A and B are obviously wrong. However answer D states “Sodium hydroxide has a higher hydroxide concentration than ammonia”. This answer is clearly correct too and is essentially a rewording of answer C since a higher hydroxide concentration will result in a higher pH value. I find it amazing that this seems to have got completely through the system without being challenged by teachers on the G2s and not being altered at the grade award meeting. There is no specific mention of this question to explain why only answer C is correct in the M2010 TZ1 Chief Examiner’s Report. If you do use this as your mock examination it will be interesting to see if any of your students comment upon it. Possibly a printing error has occurred in the papers or markscheme sold after the session had ended.¹

Perhaps this illustrates that with the best will in the world mistakes can still get through – after all examiners (and the people who print the examination papers) are only human. I am acutely aware of this myself when I put material on this site. Because I cannot use past IB questions for copyright reasons all my 500 or so multiple choice questions are brand new. I have checked them and the answers as carefully as I can but they have not been externally checked so if you do find any errors please let me know. One of the great advantages of a live website is that mistakes (once pointed out) can be rectified immediately.

¹. In fact I have just found out that it was a printing error in the CD that was sent out (so the examiners are off the hook!!). On the original paper the wording for answer D was "When the basic solutions exactly neutralize separate identical solutions of ethanoic acid, more of the ammonia solution is needed". This explains why there was no comment on this question in the Chief Examiner's Report.