Question

Which of the following reactions can occur in a voltaic cell with the generation of electron flow?

a) Zn2+ + S2- → ZnS

b) ZnCl2 + H2S→ ZnS + 2HCl

c) Zn+ CuCl2 → ZnCl2 + Cu

d) Fe3+ + PO43- → FePO4

e) none of above

Answer 1

Answer:

c) Zn + CuCl₂ ⇒ ZnCl₂ + Cu

Explanation:

Voltaic cells are devices that take advantage of reactions of oxidation and reduction to generate electrical energy.

In the oxidation, a substance loses electrons and increases its oxidation state. This reaction occurs in an electrode known as anode.

In the reduction, a substance gains electrons and decreases its oxidation state. This reaction occurs in an electrode known as cathode.

Oxidation and reduction happen simultaneously and the flow of electrons from anode to cathode is what generates an electric potential.

From the reactions in the list, "c" is the only one where oxidation and reduction are present.

 Zn oxidizes into Zn²⁺ according to the reaction:

 Zn(s) ⇒ Zn²⁺(aq) + 2 e⁻

 The oxidation state increases from 0 to 2.

 Cu²⁺ reduces to Cu according to the reaction:

 Cu²⁺(aq) + 2 e⁻ ⇒ Cu(s)

 The oxidation state decreases from 2 to 0.