Oquizy

If a different solvent is used in chromatography, what happens to the Rf values?

All Rf values increase Rf values decrease to zero Rf values may change depending on solubility Rf values remain unchanged

John is heating ethanol with a Bunsen burner. What is the most important safety precaution?

Boil it quickly for accuracy Use a strong tripod Use a water bath Wear cotton gloves

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

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 conclusion can you draw?

A contains a mixture A is pure B has three substances Solvent didn't work

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

Quiz: Chemistry - Experimental Chemistry