GCSE / O Levels Chemistry

When iron reacts with dilute hydrochloric acid, hydrogen is formed. Impurities in the iron mean
that some hydrogen sulfide gas is also formed. Hydrogen sulfide gas is soluble in water. Water
vapour can be removed from a mixture of gases using concentrated sulfuric acid.
Which diagram shows apparatus suitable to prepare a pure, dry sample of hydrogen?
A
B
C
D
iron and
hydrochloric acid
iron and
hydrochloric acid
iron and
hydrochloric acid
iron and
hydrochloric acid
=U
water
-water
11
water
concentrated
sulfuric acid
concentrated
sulfuric acid
concentrated
sulfuric acid
concentrated MM. water
sulfuric acid
2.5

Choice C is correct because:

The apparatus contains a control stopper to prevent the gas produced from escaping and both the test tubes contain inlets which allows the gases to dissolve in the aqueous medium.

The hydrogen sulfide produced is first dissolved in the water after which the hydrogen gas produced is dried by passing it through concentrated sulfuric acid.

Choice A is incorrect because the apparatus containing iron and hydrochloric acid does not have a stopper above it which will prevent the gas from escaping into the atmosphere. This means that not all of the gas produced will reach the test tube placed on the right.

Choice B is incorrect because the delivery tubes carrying the gases produced are not immersed in the aqueous medium.

Choice D is incorrect because the apparatus set up is not suitable to produce a pure, dry sample of hydrogen.

Methods of Purification and Analysis | 2022 - O/N - 5070/12 | Q2