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Solubility rules: do I have to know them for the Nuffield exam?
It is never easy to be sure quite what is required when reading a course specification (syllabus). This is illustrated by a recent e-mail exchange between two Nuffield teachers - one of whom is also has experience as an examiner. Do you agree? Please comment.
Question from a teacher
I want to know whether or not students have to know the solubility rules in Topic 1 for the Edexcel Chemistry (Nuffield) AS exams. The rules are not in the specification. However, another teacher at my school has been told at a training day that students do need to know these rules.
Answer
This is a tricky point and one which indicates a severe problem with the concept of a specification which limits the scope of examinations when there is also a published course. This is a problem for the examiners setting questions too.
In this case, the Edexcel Chemistry (Nuffield) specification says the following relevant things:
CONTENT
1.1 Chemical reactions revised, thermal decomposition, solubility,
precipitation and neutralisation.
SKILLS
d recognise thermal decomposition, precipitation, redox reactions and be able to construct balanced chemical equations (full and ionic) for simple examples, including the use of state symbols.
f recall the meaning of the terms: solution, solvent, solute and saturated solution and demonstrate understanding of the practical use of these terms in salt preparation.
Taking all these things into consideration, are the solubility rules 'in' or not? I would say the safe thing is to learn them despite the fact that the actual words 'solubility rules' do not appear. There are many other words which don't appear, either, but that is not to say that a knowledge of them will never be helpful in an exam. Knowing the solubility rules makes it much easier to be confident when writing an ionic equation for a precipitation reaction, for example.
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Robert Smith
Without solubility rules you can get by. But if you ever want to understand chemistry instead of just learning chemistry they are essential.
During my A2 chemistry coursework, which was done in an industrial situation, the solubility rules were essential in order to know the correct standard solutions to use for atomic absorbtion.
Why bother missing out on such a small learning task when it can be so beneficial?
07 May 2003
Andrew Hunt
Clearly without a general knowledge of the rules they cannot confidently write ionic equations for precipitation reactions - and that is why it is necessary to know the rules. However knowledge of the rules is not required explicitly in the specification which to me implies that you would not expect to find questions in an exam requiring students to recall and state the rules.
02 December 2002
Jackie Ellender
If the solubility rules are not learned, how can students predict the precipitates in precipitation reaction, include the correct state symbols and write the correct ionic equations?
01 December 2002
updated: 30 May 2006
