Chemistry · Oct / Nov 2020 · Paper 61 · Question 4
0620
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The question as text
A mixture contains three solid compounds: ● copper(II) sulfate ● cetyl alcohol ● silicon dioxide. The table gives some information on the solubility of these three solids. name of compound solubility in water solubility in propanone copper(II) sulfate soluble insoluble cetyl alcohol insoluble soluble silicon dioxide insoluble insoluble Plan a method to obtain a pure sample of each of the three solids, copper(II) sulfate, cetyl alcohol and silicon dioxide, from the mixture. You have access to normal laboratory apparatus. [6]
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M1 whatever method is used, suitable apparatus – such as a flask or beaker – has been used.
Copper(II) sulfate first
M2 add water (to dissolve copper sulfate) and later adds propanone (to dissolve cetyl alcohol)
M3 stir / swirl / mix
M4 filter (to remove silicon dioxide and cetyl alcohol)
M5 evaporate solvent from filtrate or description. This must be done for the solutions obtained using both solvents. M6 filter and wash / rinse residue after adding the second solvent
M7 dry residue (silicon dioxide)
OR
cetyl alcohol first
M2 add propanone (to dissolve cetyl alcohol) and later adds water (to dissolve copper(II) sulfate)
M3 stir / swirl / mix
M4 filter (to remove silicon dioxide and copper(II) sulfate)
M5 evaporate solvent from filtrate or description. This must be done for the solutions obtained using both solvents. M6 filter and wash residue after adding the second solvent
M7 dry residue (silicon dioxide)
max 6
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