CAIE A-Level Chemistry A2 37.2.1 And Understand the Terms Topic Practice

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Question 1

[Maximum number: 2]

Lactic acid, CH3CH(OH)COOH\mathrm{CH}_{3} \mathrm{CH}(\mathrm{OH}) \mathrm{COOH}, is the only monomer needed to form the polymer polylactic acid, PLA.

Question (a)

(a)

An impure sample of CH3CH(OH)COOH\mathrm{CH}_{3} \mathrm{CH}(\mathrm{OH}) \mathrm{COOH} contains pentan-3-one as the only contaminant. The mixture is analysed using gas/liquid chromatography. The pentan-3-one is found to have a longer retention time than the lactic acid.

[ 2 ]

Question (i)

(i)

Explain what is meant by retention time.

[ 1 ]

Question (ii)

(ii)

Suggest suitable substances, or types of substances, that could be used as the mobile and stationary phases.
mobile phase
stationary phase

[ 1 ]
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