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2.1 Purity and separating mixtures

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Question 14

A chemist makes a sample of a new sweetener and tests it by paper chromatography in two different solvents.

With water as the solvent, the sample gives a single spot.

With ethanol as the solvent, the sample gives two separate spots.

Which conclusion about the sweetener sample is correct?

[1]
A

The sample is pure, because it gave a single spot when water was the solvent.

B

The sample is pure, but ethanol has reacted with it to form a second substance.

C

The results cannot be trusted, because a pure substance has the same Rf value in every solvent.

D

The sample is a mixture of at least two substances that travel the same distance in water.

Markscheme

2.1 Purity and separating mixtures Questions

  1. GCSE
  2. /Chemistry
  3. /2.1 Purity and separating mixtures

102 exam-style questions on OCR GCSE Chemistry 2.1 Purity and separating mixtures, covering 2.1.1 Pure substances and melting point data, 2.1.2 Relative formula mass and empirical formula, 2.1.3 Formulations as useful mixtures, 2.1.4 Techniques for separating mixtures, and 2.1.5 Chromatography and Rf values. Each one has a worked solution and a mark scheme showing where the marks go.

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