reactivity series

Question 1

2:15 understand how metals can be arranged in a reactivity series based on their reactions with: water and dilute hydrochloric or sulfuric acid

Answer 1

many metals are too low in the reactivity series to have a reaction with water, so dilute hydrochloric acid or dilute sulfuric acid can be used.

react with water:
potassium
sodium
lithium
calcium

react with acid:
potassium
sodium
lithium
calcium
magnesium
aluminium
zinc
iron

The order of reactivity can be determined by adding acid to different metals and observing the rate of reaction.

For example, when hydrochloric acid is added to iron (Fe) then bubbles of hydrogen are produced slowly. However, if the same acid is added to zinc (Zn) then bubbles will be produced more quickly. This tells us that zinc is more reactive than iron.

Question 2

preventing iron from rusting

Answer 2

barrier methods:
Rusting may be prevented by stopping the water and oxygen getting to the iron with a barrier of grease, oil, paint or plastic.

galvanising:
(coating in zinc) also prevents water and oxygen getting to the iron, but with galvanising even if the barrier is broken the more reactive zinc corrodes before the less reactive iron. During the process, the zinc loses electrons to form zinc ions.

sacrificial protection:
Zinc blocks are attached to iron boat hulls and underground pipelines to act as sacrificial anodes. Zinc is more reactive than iron, so oxygen in the air reacts with the zinc to form a layer of zinc oxide instead of the iron.

Question 3

2:21 practical: investigate reactions between dilute hydrochloric and sulfuric acids and metals (e.g. magnesium, zinc and iron)

Answer 3

metal + acid → salt + hydrogen when metal is above hydrogen in the reactivity series

this is a displacement reaction

e.g: magnesium and dilute hydrochloric acid
- There is a rapid fizzing and a colourless gas is produced. This gas pops with a lighted splint, showing the gas is hydrogen.
- The reaction mixture becomes warm as heat is produced (exothermic).
- The magnesium disappears to leave a colourless solution of magnesium chloride.

If more reactive metals are used instead of magnesium the reaction will be faster so the fizzing will be more vigorous and more heat will be produced.