Electrolysis-Electrode potential

What is electrolysis?

The breaking down of a compound into its elements using an electric current.

What are the products at cathode and anode during electrolysis of molten ZnCl2?

Cathode: Zn(s); Anode: Cl2(g).

In electrolysis, which electrode is the cathode and what happens there?

The cathode is the negative electrode; reduction happens there (cations gain electrons).

What happens at the anode during electrolysis?

Oxidation occurs; anions lose electrons.

What factors determine which ions are discharged in aqueous electrolysis?

Relative electrode potential and ion concentration.

Why is water important in aqueous electrolysis?

It contributes H⁺ and OH⁻ ions that can be discharged depending on E° values and concentration.

Which gas is formed at the cathode in electrolysis of NaF(aq)?

Hydrogen gas, because H⁺ has a higher E° than Na⁺.

What product forms at the anode in concentrated NaF(aq)?

Fluorine gas (F₂), due to higher concentration and lower E° value.

What is Faraday’s law of electrolysis?

Amount of substance formed is proportional to current × time (Q = It).

How many coulombs are needed to deposit 1 mol of Mg from Mg²⁺?

2 × 96,500 = 193,000 C.

How can L (Avogadro's constant) be experimentally found via electrolysis?

By determining the charge to deposit a known mass of metal and comparing it with the electron charge.

How much charge is needed to produce 1 mol of hydrogen gas?

2 × 96,500 = 193,000 C.

How do you find volume of gas produced?

Use mol = Q/(nF), then multiply by 24.0 dm³/mol at RTP.

What is a standard electrode potential (E°)?

The voltage of a half-cell compared to a standard hydrogen electrode under standard conditions.

What are standard conditions for E° measurements?

298 K, 1 atm, 1.00 mol/dm³ concentration.

How is E°cell calculated?

E°cell = E°(right) - E°(left) or E°(reduction) - E°(oxidation).

Which electrode is the positive pole in a cell?

The one with the more positive E° (where reduction happens).

What does a positive E°cell mean?

The reaction is feasible (spontaneous).

What is the direction of electron flow in a cell?

From the more negative electrode (oxidation) to the more positive electrode (reduction).

Write the simplified Nernst equation.

E = E° + (0.059/z) log([oxidised]/[reduced]).

What happens to E if [oxidised] increases?

E becomes more positive.

Why are solids and gases not included in the Nernst equation?

Their concentrations are constant (taken as 1).

How do you calculate ΔG from E°cell?

ΔG = –nFE°cell.