An organic chemist synthesises a sample of paracetamol (literature melting point 169 ∘C169\ ^\circ\text{C}169 ∘C). To assess the purity of the recrystallised product, she performs thin-layer chromatography (TLC) and measures its melting point range. Which set of results should the chemist expect if the sample is completely pure?
TLC chromatogramMelting point range (∘C)ATwo distinct spots168–169BSingle spot168–169CSingle spot158–165DTwo distinct spots158–165 \begin{array}{|c|c|c|} \hline & \textbf{TLC chromatogram} & \textbf{Melting point range } (^\circ\text{C}) \\ \hline \textbf{A} & \text{Two distinct spots} & 168\text{--}169 \\ \hline \textbf{B} & \text{Single spot} & 168\text{--}169 \\ \hline \textbf{C} & \text{Single spot} & 158\text{--}165 \\ \hline \textbf{D} & \text{Two distinct spots} & 158\text{--}165 \\ \hline \end{array} ABCDTLC chromatogramTwo distinct spotsSingle spotSingle spotTwo distinct spotsMelting point range (∘C)168–169168–169158–165158–165A\textbf{A}A
B\textbf{B}B
C\textbf{C}C
D\textbf{D}D
46 exam-style questions on OCR GCSE Chemistry Purity and separating mixtures. Each one has a worked solution and a mark scheme showing where the marks go.