4️⃣ PAG 1: Reactivity trend

Question 1

Safety

Answer 1

● Magnesium is very flammable so ensure there are no open flames in the laboratory.
● Eye protection must be worn at all times.
● Wash hands after coming into contact with any of the chemical substances used.
● Wash hands after touching the metal pieces, especially lead foil.
● Dispose of each mixture by passing it through a sieve into a waste beaker.

Question 2

Equipment

Answer 2

Equipment
•	spotting tile, with at least 16 depressions (or two smaller tiles)
•	dropping pipettes
•	strips of magnesium, zinc, iron, copper	
•	magnesium sulfate solution
•	iron(II) sulfate solution
•	copper(II) sulfate solution
•	zinc sulfate solution

Question 3

How are we going to deduce the order of reactivity of the 4 metals - magnesium, zinc, iron, copper

(Setting scene)

Answer 3

Some metals are more reactive than others. When a strip of metal is added to a solution containing another metal compound, the more reactive metal can displace (take the place of) the less reactive metal from its compound.
You are going to carry out a series of metal displacement reactions and use your observations to deduce the order of reactivity of the four metals you have used.

Question 4

Method - 4 stages

Answer 4

1 Using a dropping pipette, put a few drops of copper(II) sulfate solution into four of the wells in the spotting tile.
2 Place a strip of magnesium into the first well of liquid, zinc into the second, iron into the third and copper into the fourth. Leave for about a minute.
3 Note down any changes in the table below. If there is no change, write ‘No change’.
4 Repeat these steps replacing the copper sulfate solution with each of the other three solutions in turn. Use a fresh dropper for each solution.

Question 5

PMT observations and analysis - using magnesium, iron, copper, and lead (instead of zinc)

Answer 5

● The observation results show that the order of reactivity is:
Cu

Question 6

Key points PMT

Answer 6

Key points
● If there is no change observed when the metal is added to the solution, then the solid metal is less reactive than the metal in the aqueous ionic compound.
● If the metal formed in the drop of iron sulfate moves when a magnet is held near it, iron has been displaced from the iron sulfate solution.