Nickel (II) salts, like nickel (II) sulfate, are classed as category 1 carcinogens and colbalt (II) salts, like cobalt (II) chloride, are category 2 carcinogens. As such, neither of these two kinds of salts are recommended for use in experiments at school.
What follows is a description of some displacement reactions which were carried out on a microscale in order to minimise the hazards like the ones mentioned above. The experiments involved adding magnesium ribbon to small volumes of aqueous solutions of some transition metal salts.
Small pieces of magnesium ribbon were dropped into approximately 1.5ml of each of the following solutions:
1M manganese (II) sulfate
0.5M iron (II) chloride
1M cobalt (II) chloride
1M nickel (II) sulfate
0.5M copper (II) sulfate
0.5M zinc sulfate.
After several minutes a small neodymium magnet was waved over the magnesium metal strips. The results are summarised in the gif animations below.
The animations were constructed from a movie of the reactions which can be viewed on You Tube here.
Which pieces of magnesium were attracted to the neodymium magnet and why?