24.1 A2 Level

Electrolysis

8 flashcards to master this topic

Key Concept Flip

State the three factors that determine the products formed during the electrolysis of an aqueous solution.

Answer Flip

The products depend on: 1) The state of the electrolyte (aqueous vs. molten), 2) The position of the ions in the electrochemical series (electrode potential), and 3) The concentration of the ions in solution.

Definition Flip

Define the Faraday constant (F).

Answer Flip

The Faraday constant (F) is the magnitude of electric charge per mole of electrons. It is related to the Avogadro constant (L) and the elementary charge (e) by the equation: F = Le.

Calculation Flip

What is the equation used to calculate the quantity of charge (Q) passed during electrolysis?

Answer Flip

The quantity of charge (Q) is calculated using the equation: Q = It, where I is the current (in amperes) and t is the time (in seconds).

Key Concept Flip

How can electrolysis be used to determine the Avogadro constant?

Answer Flip

By electrolyzing a known mass of a substance (

Example: copper), measure the charge required to deposit one mole of the substance. Using F = Le, and knowing the charge of an electron (e), Avogadro constant L can be calculated: L = F/e.
Calculation Flip

What volume of hydrogen gas (at RTP) is produced during the electrolysis of water by a current of 2A for 30 minutes?

Answer Flip

First calculate Q = It = 2A * (30 * 60)s = 3600 C. Then find moles of electrons: moles = Q/F = 3600/96500 = 0.0373 mol. H₂ requires 2 electrons: moles of H₂ = 0.0373/2 = 0.0186 mol. Finally, volume = moles * 24000 cm³ = 447 cm³.

Key Concept Flip

During the electrolysis of concentrated NaCl(aq), which product is preferentially discharged at the anode, and why?

Answer Flip

Chlorine gas (Cl₂) is preferentially discharged at the anode because it has a lower (less positive) electrode potential compared to oxygen from water, and the high concentration of Cl⁻ further favors its discharge.

Key Concept Flip

Explain why different products may be obtained when electrolyzing molten NaCl compared to aqueous NaCl.

Answer Flip

In molten NaCl, only Na⁺ and Cl⁻ are present, so Na(l) and Cl₂(g) are produced. In aqueous NaCl, H₂O is present and can be reduced to H₂(g), while either Cl⁻ or H₂O can be oxidized, depending on concentration (Cl⁻ favored when concentrated).

Definition Flip

Define electrolysis.

Answer Flip

Electrolysis is the process of using an electric current to drive a non-spontaneous chemical reaction. It occurs in an electrolytic cell, which consists of electrodes immersed in an electrolyte.

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23.2 Enthalpies of solution and hydration 24.2 Standard electrode potentials E