Experimental chemistry (Combined Science)

A gas X is insoluble in water and less dense than air. An impure supply of X contains water vapour and a water-soluble impurity. In which order should pieces of apparatus be joined together to collect a pure dry sample of X?

• 1, 2, 3, 4

• 1, 2, 3, 5

• 1, 3, 2, 5

• 1, 3, 2, 4

A student tries to separate a mixture of ethanol and water by fractional distillation using the apparatus shown. Which error has the student made?

• The condenser is at the wrong angle

• The thermometer is in the wrong position

• The top of the conical flask should be open

• The water enters the condenser in the wrong place

The diagram shows apparatus used to separate hexane (boiling point, 70^oC) and heptane (boiling point, 98^oC). Which graph would be obtained if the temperature at point T was plotted against the total volume of distillate collected?

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Which piece of apparatus would be most suitable to measure accurately the volume of acid needed to neutralize 25.0 cm³ of an alkali.

• A

• B

• C

• D

The diagrams show three sets of apparatus. What apparatus would be used to obtain separate samples of sand and salt from a mixture of sand and seawater?

• 1 only

• 1 and 3

• 2 and 3

• 3 only

A gas Y, is less dense than air, very soluble in water and is an alkali.

Which method is used to collect a dry sample of the gas?

• A

• B

• C

• D

Gas Y is less dense than air and very soluble in water, forming an alkaline solution. Which method is used to collect a dry sample of the gas?

• A

• B

• C

• D

A gas, X, is less dense than air and insoluble in water.

Which method cannot be used to collect the gas?

• A

• B

• C

• D

Samples of tinned apricots, beans, corn and tomatoes are tested for additives by chromatography.

The chromatograms are compared with those of three artificial additives, P, Q and R. The results are as follows.

Which tinned food does not contain any artificial additives?

• Apricots

• Beans

• Corn

• Tomatoes

Which property shows that a liquid is pure?

• It turns anhydrous copper(II) sulfate blue

• It is colourless and odourless

• It has no effect on red or blue litmus paper

• It boils at a fixed temperature at a given pressure