Question

In the cell \[\text{Ag}|\text{A}{{\text{g}}^{\text{+}}}||\text{C}{{\text{u}}^{\text{2+}}}|\text{Cu}\] containing \[\text{1 M C}{{\text{u}}^{\text{2+}}}\]and \[\text{1 M A}{{\text{g}}^{\text{+}}}\] ions, 9.65 ampere current is passed for 1 hour. This question has multiple correct options : a.) Ag will oxidise to \[\text{A}{{\text{g}}^{\text{+}}}\] and new\[\text{ }\!\!~\!\!\text{ }\left[ \text{A}{{\text{g}}^{\text{+}}} \right]\text{ = 1}\text{.36 M}\]
b.) \[\text{A}{{\text{g}}^{\text{+}}}\] will reduce to Ag and new \[\left[ \text{A}{{\text{g}}^{\text{+}}} \right]\text{ = 0}\text{.64 M}\]
c.) \[\text{C}{{\text{u}}^{\text{+2}}}\] will reduce to Cu and new \[\left[ \text{C}{{\text{u}}^{\text{+2}}} \right]\text{ = 0}\text{.82 M}\]
d.) Cu will oxidise to \[\text{C}{{\text{u}}^{\text{+2}}}\] and new \[\left[ \text{C}{{\text{u}}^{\text{+2}}} \right]\text{ = 0}\text{.82 M}\]

Answer 1

Hint: We should know the importance of Oxidation - Reduction (redox) reactions before solving the numerical. Redox reactions are the principal sources of energy on this planet, both natural or biological and artificial.

Complete answer:
Passage of current through given cell Ag will oxidize to \[\text{A}{{\text{g}}^{\text{+}}}\] and \[\text{C}{{\text{u}}^{\text{+}}}\],and it will be reduced to Cu, \[\text{C}{{\text{u}}^{\text{+}}}\]
$\dfrac{\text{w}}{\text{E}}\text{=}\dfrac{\text{i}\text{.t}}{\text{96500}}\text{=}\dfrac{\text{9}\text{.65 }\!\!\times\!\!\text{ 3600}}{\text{96500}}$
$\text{=0}\text{.36 eq}\text{. of A}{{\text{g}}^{+}}=0.36\text{ mol of A}{{\text{g}}^{+}}$
$\text{=0}\text{.36 eq}\text{. of C}{{\text{u}}^{\text{+}}}$
$\text{=}\dfrac{\text{0}\text{.36}}{\text{2}}\text{ mole of C}{{\text{u}}^{\text{+}}}\text{ (as mole = }\dfrac{\text{equivalent}}{\text{valency}}\text{)}$
$\therefore \left[ \text{A}{{\text{g}}^{\text{+}}} \right]\text{ = 1 + 0}\text{ .36 = 1}\text{.36 M}$
    $\left[ C{{u}^{\text{+}}} \right]\text{ = 1}\text{.0 - 0}\text{.36 = 1}\text{.36 M}$

So, we can say that from the above mentioned process we can see, Option A is the correct answer.

Note:
We should know that oxidation of molecules by removal of hydrogen or combination with oxygen normally liberates large quantities of energy.
Redox reactions occur because the products will be at a lower total energy than the reactants.
Even if we know nothing of electrons and oxidation states, redox reactions would still occur because a product will be spontaneously being at a lower chemical potential energy.
We should also have an idea that redox reactions are characterized by the actual or formal transfer of electrons between chemical species, most often with one species (the reducing agent) undergoing oxidation (losing electrons) while another species (the oxidizing agent) undergoes (reduction gains electron).