A piece of magnesium disappears in CuCl2 solution

Question

I want you to mention in the results of the experiment that since the reaction that occurred is the dismantling of chemical bonds, it will be an exothermic reaction, and explain it, etc.

Answer 1

Maram,

You asked a similar question 3 days ago, and I provided an answer (see below). The reaction taking place is

Mg(s) + CuCl2(aq) ==> MgCl2 + Cu(s)

The breaking of bonds involves the bonds holding the atoms of Mg together (metallic bonds) and those holding CuCl2 together (ionic bonds). This requires energy. Then when new bonds form between Mg and Cl, and between atoms of Cu, energy is released. If the reaction is exothermic (heat given off), then that means that more energy is released during the forming of the new bonds than was used to break the original bonds.

I'm guessing it was a lab on oxidation and reduction. If you had a solid piece of magnesium (Mg) and some Cu²⁺ in solution as CuCl₂, what do you think might happen? Look up the reduction potentials for both Mg and Cu (Mg²⁺ and Cu²⁺). I think you'll see that Cu²⁺ will be reduced before Mg²⁺, so that means in the situation you have, Cu²⁺ will be reduced to Cu(s) and Mg(s) will be oxidized to Mg²⁺ and go into solution. So the solid Mg will disappear. But you should also see solid copper Cu(s) appear.

Mg(s) + Cu²⁺(aq) ==> Mg²⁺(aq) + Cu(s)