Separation Technique Pure Chem

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A liquid ester used to flavour food is believed to be impure. What would be the best way of testing its purity?

• filter it

• measure its boiling point

• use paper chromatography

• evaporate it to dryness

A mixture contains two substances. What property must the two substances have for them to be separated by paper chromatography?

• Both substances must be soluble in the chromatography solvent.

• Both substances must have low boiling points.

• Both substances must be coloured.

• Both substances must be solid at room conditions.

When heated steadily, an impure solid S starts melting at 131^oC and becomes completely molten at 136^oC. The melting points of four pure solids are given below. Which one could apply to S?

• 130^oC

• 131^oC

• 135^oC

• 137^oC

Compound Q melts at 78^oC and boils at 124^oC and is not soluble in water. Which apparatus can be used to obtain pure Q from a mixture of Q and water.

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The diagram shows apparatus used to separate a mixture of two liquids with boiling points 85^oC and 110^oC.

Which graph would be obtained if the temperature at point P was plotted against the total volume of distillate produced?

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Substance S contains one of the three substances X, Y or Z. Two chromatograms of the four substances, using different solvents, are shown in the diagrams.

What does substance S contain?

• X only

• Z only

• X and Z

• Y and Z

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• 1,2,3,4

• 3,4,1,2

• 3,1,2 ( omit 4)

• 4,1,2 ( omit 3)