Explain4 marksStandard
The hydrogen halides are , , and . Their thermal stability decreases down the group: is the most stable and is the least stable.
Explain this trend in terms of bond strengths.
CAIE A Level Chemistry 9701 · Group 17
Group 17: explain question
How this question is marked
4 marks, so the mark scheme is looking for about 4 separate creditworthy points. Making the same point twice in different words earns it once.
Explain means: Give the reasons or the mechanism: why or how something happens. Link each point to the next with because, so or which means. A list of facts with no links usually loses the reasoning marks.
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