Why must the solvent level begin below the spots on a chromatography baseline?
The solvent would move up the paper too quickly
The spots would dissolve into the solvent in the beaker
The solvent front could not be marked clearly
The pencil line would dissolve and mix with the spots
107 exam-style questions on Edexcel GCSE Chemistry 3.2 Methods of separating and purifying substances, covering 3.2.1 Pure substances and mixtures, 3.2.2 Techniques for separating mixtures, 3.2.3 Paper chromatography and Rf values, and 3.2.4 Making water potable. Each one has a worked solution and a mark scheme showing where the marks go.