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

There may be differences between the identity and/or concentrations of chemicals and materials 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

The confidential instructions may specify 0.1 mol dm^-3 hydrochloric acid to be identified as FB1 because it is inexpensive and widely available. However, the question paper may describe FB1 as 1 mol dm^-3 propanoic acid which better suits the context of the exam question.