IGCSE Chemistry : Experimental Techniques

The diagrams show four pieces of laboratory equipment.

• A

• B

• C

• D

During an experiment a measurement is recorded in cm³ . Which apparatus is used?

• balance

• measuring cylinder

• stopclock

• thermometer

A student carried out paper chromatography on a mixture of amino acids. The student sprayed the dried chromatogram with a locating agent. What is the function of the locating agent?

• to dissolve the amino acids

• to form coloured spots with the amino acids

• to preserve the amino acids

• to stop the amino acids reacting

25 cm³ of an alkali are added to 20 cm³ of an acid. The temperature change is measured. Which apparatus is not needed in the experiment?

• 25 cm³ measuring cylinder

• 100 cm³ beaker

• balance

• thermometer

The painkiller paracetamol is synthesised from 4-aminophenol. Chromatography was carried out on an impure sample of paracetamol. The results are shown (not drawn to scale).

The sample of paracetamol was contaminated with 4-aminophenol only. What is the R_f value of 4-aminophenol?

• 0.49

• 0.65

• 0.74

• 1.35

A student put 25.0 cm³ of dilute hydrochloric acid into a conical flask. The student added 2.5 g of solid sodium carbonate and measured the change in temperature of the mixture. Which apparatus does the student need to use to obtain the most accurate results?

• balance, measuring cylinder, thermometer

• balance, pipette, stopwatch

• balance, pipette, thermometer

• burette, pipette, thermometer

The results obtained from a chromatogram are shown.

Which row gives the R_f values of substance X and substance Y?

• A

• B

• C

• D

A student mixes 25cm³ samples of dilute hydrochloric acid with different volumes of aqueous sodium hydroxide. In each case, the student measures the change in temperature to test if the reaction is exothermic. Which piece of apparatus is not needed?

• A

• B

• C

• D

A solid X is purified in five steps. The first four steps of the purification are shown in the diagram.

In step 5, how is a pure sample of solid X obtained from mixture Y?

• dissolving

• distillation

• evaporating

• filtering

Information about the solubility of four solids, P, Q, R and S, is given in the table.

A student attempted to separate mixtures of these solids using the following method.

1 Add the mixture to a beaker of water and stir.

2 Filter the mixture.

3 Crystallise one of the solids from the filtrate. Which of the following mixtures could not be separated by this method?

• a mixture of P and R

• a mixture of Q and P

• a mixture of Q and R

• a mixture of R and S