Redox Reactions

The given redox reaction can be depicted as

Zn (s) + 2Ag⁺ (aq) → Zn²⁺ (aq) + 2Ag (s)
Since Zn gets oxidised to Zn²⁺ ions, and Ag⁺ gets reduced to Ag metal, therefore,

Oxidation occurs at the zinc electrode and reduction occurs at the silver electrode. Thus, galvanic cell corresponding to the above redox reaction may be depicted as:

Zn|Zn²⁺ (aq) | Ag⁺ (aq) | Ag

(i) Zinc electrode is negatively charged because oxidation occurs at the zinc electrode (i.e. electrons accumlulate on the zinc electrode)

(ii) The ions carry current. The electrons flow from Zn to Ag electrode while the current flows from Ag to Zn electrode.

(iii) Reaction occurring at each electrode are:

Zn (s) → Zn²⁺ (aq) + 2e^-

Ag⁺ (aq) + e^- → Ag (s)

(i) An aqueous solution of AgNO₃?  with silver electrodes.
At cathode: Silver ions have lower discharge potential than hydrogen ions. Hence, silver ions will be deposited in preference to hydrogen ions.

At anode: Silver anode will dissolve to form silver ions in the solution.
Ag → Ag⁺ + e⁻

(ii) An aqueous solution of AgNO_3?  with platinum electrodes.

At cathode: Silver ions have lower discharge potential than hydrogen ions. Hence, silver ions will be deposited in preference to hydrogen ions.

At anode: Hydroxide ions having lower discharge potential will be discharged in preference to nitrate ions. Hydroxide ions will decompose to give oxygen.
4OH⁻ (aq) → 2H₂? O (l) + O₂? (g) + 4e⁻

(iii) A dilute solution of H₂? SO₄?  with platinum electrodes.

At cathode: 2H⁺ + 2e⁻ → H₂? (g)

At anode: Hydroxide ions having lower discharge potential will be discharged in preference to sulphate ions. Hydroxide ions will decompose to give oxygen.
4OH⁻ (aq) → 2H₂? O (l) + O₂? (g) + 4e⁻

(iv) An aqueous solution of CuCl₂?  with platinum electrodes

At cathode: Cupric ions will be reduced in preference to protons
Cu²⁺ + 2e⁻ → Cu

At anode: Chloride ions will be oxidized in preference to hydroxide ions
2Cl⁻ → Cl₂? + 2e⁻

(a) F. Fluorine being the most electronegative element shows only a -ve oxidation state of -1.

(b) Cs. Alkali metals because of the presence of a single electron in the valence shell, exhibit an oxidation state of +1.

(c) I. Because of the presence of seven electrons in the valence shell, I shows an oxidation state of -1 (in compounds of I with more electropositive elements such as H, Na, K, Ca, etc.) or an oxidation state of +1 compounds of I with more electronegative elements, i.e., O, F, etc.) and because of the presence of d-orbitals it also exhibits +ve oxidation states of +3, +5 and +7.

(d) Ne. It is an inert gas (with high ionization enthalpy and high positive electron gain enthalpy) and hence it neither exhibits -ve nor +ve oxidation states.