Question 19M.1.hl.TZ2.31

Another challenging question with a high discrimination index. 57 % of the candidates were able to identify the electrode products during the electrolysis of concentration KBr (aq). The most commonly chosen distractor was C where K was the product at the cathode (instead of H₂). Some teachers commented that the data booklet was needed to solve this question and others said “concentrated” was vague. But the effect of concentration is clearly stated in the syllabus and does not need the data booklet to be determined. As for the cation, potassium is known as a reactive metal according to the periodic trends and should have been easy to recognize as more reactive than hydrogen. Similar questions have appeared in past papers.