Explain how variations in the strength of the interactions between atoms, molecules or ions in the mobile and stationary phases can be used to separate components.

A student performs thin-layer chromatography (TLC) using a silica gel plate (polar stationary phase) and hexane (non-polar mobile phase) to separate a mixture of two compounds: hexanoic acid (polar) and hexane (non-polar). Explain why hexanoic acid travels a shorter distance than hexane on the TLC plate.

A mixture of three compounds is separated using thin-layer chromatography (TLC) with a polar stationary phase (silica gel) and a non-polar mobile phase (hexane). The compounds have the following properties: • Compound P: non-polar hydrocarbon • Compound Q: moderately polar alcohol • Compound R: highly polar carboxylic acid Which compound would travel the greatest distance up the TLC plate?

In paper chromatography, a mixture of three amino acids is separated using a polar mobile phase. The amino acids have the following side chains: glycine (–H), alanine (–CH₃), and leucine (–CH₂CH(CH₃)₂). Which amino acid travels the greatest distance up the chromatography paper?