Is lead less reactive than hydrogen?

Observe the diagram showing a copper rod kept immersed in silver nitrate solution.

a. What is the colour change of the solution?
b. Write the balanced chemical equation for the reaction.

Answer the following:

Why are highly reactive metals such as Aluminium is used as reducing agents?

Food cans are coated with tin and not with zinc because

Which of the following set of reactions will NOT occur?

I. ${\mathrm{MgSO}}_4\left(\mathrm{aq}\right) + \mathrm{Fe}\left(\mathrm{s}\right) \to {\mathrm{FeSO}}_4\left(\mathrm{aq}\right) + \mathrm{Mg}\left(\mathrm{s}\right)$

II. ${\mathrm{CuSO}}_4\left(\mathrm{aq}\right) + \mathrm{Fe}\left(\mathrm{s}\right) \to {\mathrm{FeSO}}_4\left(\mathrm{aq}\right) + \mathrm{Cu}\left(\mathrm{s}\right)$

III. ${\mathrm{MgSO}}_4\left(\mathrm{aq}\right) + \mathrm{Cu}\left(\mathrm{s}\right) \to {\mathrm{CuSO}}_4\left(\mathrm{aq}\right) + \mathrm{Mg}\left(\mathrm{s}\right)$

IV. ${\mathrm{CuSO}}_4\left(\mathrm{aq}\right) + \mathrm{Zn}\left(\mathrm{s}\right) \to {\mathrm{ZnSO}}_4\left(\mathrm{aq}\right) + \mathrm{Cu}\left(\mathrm{s}\right)$

Arrange the following according to the instructions given in bracket:

$\mathrm{K}, \mathrm{Pb}, \mathrm{Ca}, \mathrm{Zn}$. (In the increasing order of the reactivity)