A student has an aqueous solution containing two dissolved dyes, one blue and one yellow. The dyes have different polarities, and the student wants to determine whether the sample contains one dye or a mixture. Which technique best accomplishes this separation and identification task?
- Simple distillation, because dyes will vaporize at different temperatures
- Filtration, because dyes can be trapped by filter paper pores
- Paper chromatography, because components travel different distances based on interactions (correct answer)
- Decanting, because the denser dye settles out first in water
- Evaporation to dryness, because each dye crystallizes in separate layers
Explanation: This question tests the skill of identifying a chromatographic technique to separate and analyze dissolved components in a solution based on differences in polarity. Paper chromatography is best because the dyes have different polarities, causing them to interact differently with the stationary phase (paper) and mobile phase (solvent), resulting in separation into distinct bands for identification. If multiple spots appear, it indicates a mixture; a single spot would suggest one dye. This method allows visualization of whether the sample is pure or mixed without destroying the components. Simple distillation (choice A) is a tempting distractor but incorrect because dyes are nonvolatile solids with high boiling points, misconstruing that distillation separates based on volatility rather than polarity in solutions. For analyzing mixtures of solutes with similar physical properties but different intermolecular interactions, chromatography is a key strategy to achieve separation and identification.