Oquizy

Why must the solvent front be marked immediately after removing the chromatogram?

It helps identify unknown compounds Paper will tear during drying Solvent continues to evaporate, altering results Spots will dissolve again

Rf value of an unknown spot is 0.72. Compare to reference Rf list:
Glucose: 0.50
Caffeine: 0.72
Ethanol: 0.95
What is the likely substance?

Caffeine Ethanol Glucose Mixture

What is the purpose of chromatography in a purity test?

To determine the number of components in a mixture To extract a colourless compound To measure melting point To separate a solid from a liquid

Which of the following suggests a pure substance?

Boils at different temperatures each trial Changes colour before boiling Melts over a wide range Melts sharply at a fixed temperature

Xinyi are testing the effect of concentration on rate of reaction. Which is the best experimental control?

Changing temperature each time Keeping volume and temperature constant Measuring pH after every test Using different acids

John measures the boiling point of an unknown liquid and finds it boils between 72°C and 76°C. Which statement is false?

It can be a solid at room temperature It is a mixture Its melting point is 43°C The substance is pure

Quiz: Chemistry - Experimental Chemistry