A forensic scientist uses thin-layer chromatography (TLC) to analyze the ink components of a blue ballpoint pen, using a non-polar hydrocarbon solvent as the mobile phase. One of the major ink pigments remains at the origin and does not travel up the chromatography plate.
Suggest one modification to the mobile phase that would allow the scientist to resolve this pigment and calculate its Rf R_f\,Rf value.
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.