Why are there differences between chemicals in the confidential instructions and the question paper?

For some syllabuses, there may be differences between the identity and/or concentrations of chemicals in the confidential instructions and those on the question paper. This is perfectly normal, and candidates must not be told the details from the confidential instructions. Differences may be for safety reasons, or so you do not have to find a less widely available chemical.

Example for Chemistry

The confidential instructions may specify 0.1 mol / dm³ hydrochloric acid to be identified as A because it is inexpensive and widely available. However, the question paper may describe A as 1 mol / dm³ propanoic acid which better suits the context of the exam question.