Chemistry 9701 · AS & A Level · Equilibria

Equilibria — practice question

(a)[2]

Explain what the term partition coefficient means.

(b)[2]

A $20\,\text{cm}^3$ volume of ethoxyethane was shaken with $75\,\text{cm}^3$ of an aqueous solution containing $5.00\,\text{g}$ of an organic compound, $J$, in $75\,\text{cm}^3$ of water, and $2.14\,\text{g}$ of $J$ was found in the ethoxyethane layer. Calculate the partition coefficient, $K_{\text{partition}}$, of $J$ between ethoxyethane and water.

(c)[2]

In a different experiment, $10\,\text{cm}^3$ of ethoxyethane were shaken with $75\,\text{cm}^3$ of an aqueous solution containing $5.00\,\text{g}$ of $J$, after which the layers were separated. The aqueous layer was then shaken with a second $10\,\text{cm}^3$ portion of ethoxyethane and separated again. The two organic layers were then mixed. Use the $K_{\text{partition}}$ value you found in part (b) to calculate the total mass of $J$ removed by this method.

(d(i))[1]

Identify the mobile phase in paper chromatography.

(d(ii))[1]

Suggest the type of liquid used as the stationary phase in gas/liquid chromatography.

(d(iii).1)[2]

State what you would measure in order to distinguish the components in the mixture in paper chromatography.

(d(iii).2)[2]

State what you would measure in order to distinguish the components in the mixture in gas/liquid chromatography.

(e)[1]

Three compounds were separated by paper chromatography using a non-polar solvent, and the chromatogram obtained is shown. Identify which compound produced each spot.

Worked solution & mark scheme

This 13-mark question has a full step-by-step worked solution and mark scheme. One marking point: Meaning of partition coefficient

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