Chapter 6: Electro Chemistry Flashcards
(19 cards)
Define electrolysis.
Electrolysis is the chemical decomposition of a compound by passing an electric current through it in the molten or aqueous state.
This process is commonly used in various applications, including electroplating and the production of chemical compounds.
What happens at the cathode during the electrolysis of molten NaCl?
The metal cation is reduced (Na⁺ + e⁻ → Na).
Reduction involves the gain of electrons by the ion.
What occurs at the anode during the electrolysis of molten NaCl?
The non-metal anion is oxidised (Cl⁻ → ½Cl₂ + e⁻).
Oxidation involves the loss of electrons by the ion.
Describe the competition in aqueous electrolysis.
In aqueous solutions, water and ions compete. Use reactivity series to predict which is discharged.
The reactivity series helps determine which species will undergo oxidation or reduction.
What are oxidation and reduction half-equations?
Half-equations show electron transfer during oxidation and reduction.
Example: Cu²⁺ + 2e⁻ → Cu (reduction) and 2Cl⁻ → Cl₂ + 2e⁻ (oxidation).
What are the products of electrolysis of dilute sulfuric acid (H₂SO₄)?
H₂ at the cathode, O₂ at the anode.
This reaction illustrates the decomposition of water, where hydrogen gas is produced at the negative electrode.
What are the products of electrolysis of aqueous sodium chloride (NaCl)?
H₂ at the cathode, Cl₂ at the anode.
This process also demonstrates the competition between water and chloride ions.
What occurs during the electrolysis of copper(II) sulfate solution (CuSO₄) with inert electrodes?
Cu at the cathode, O₂ at the anode.
This setup allows for the deposition of copper metal onto the cathode.
What happens to the mass of electrodes when using copper electrodes in copper(II) sulfate electrolysis?
The mass of the anode decreases, and the mass of the cathode increases.
This is due to the transfer of copper ions from the anode to the cathode.
Define oxidation in terms of electron transfer.
Oxidation is the loss of electrons or increase in oxidation number.
This definition emphasizes the role of electron flow in chemical reactions.
Define reduction in terms of electron transfer.
Reduction is the gain of electrons or decrease in oxidation number.
It is the opposite process of oxidation.
What is an oxidising agent?
An oxidising agent is a substance that gains electrons (is reduced).
Oxidising agents facilitate the oxidation of other substances.
What is a reducing agent?
A reducing agent is a substance that loses electrons (is oxidised).
Reducing agents facilitate the reduction of other substances.
How do you deduce oxidation numbers in a reaction?
Identify changes in oxidation states of elements during the reaction.
Example: In Fe₂O₃ + 3CO → 2Fe + 3CO₂, Fe changes from +3 to 0 (reduction) and C from +2 to +4 (oxidation).
What are the steps to balance ionic half-equations?
- Balance atoms 2. Balance O with H₂O 3. Balance H with H⁺ (or OH⁻ in base) 4. Balance charge with e⁻ 5. Combine half-equations.
These steps ensure that mass and charge are conserved in redox reactions.
Define standard electrode potential (E°).
The voltage measured when a half-cell is connected to the standard hydrogen electrode under standard conditions (298 K, 1 atm, 1 mol dm⁻³).
This standardization allows for comparison between different half-cells.
What is the standard hydrogen electrode (SHE)?
The reference electrode with a standard electrode potential of E° = 0.00 V.
It is used as a baseline for measuring the potentials of other electrodes.
How do you predict the feasibility of redox reactions using E° values?
The more positive E°, the stronger the oxidising agent. Electrons flow from more negative to more positive E°.
This concept is crucial for understanding the spontaneity of chemical reactions.
How do you calculate standard cell potentials?
E°cell = E°(cathode) – E°(anode).
The cathode is where reduction occurs, and the anode is where oxidation occurs.
