ELECTROLYSIS -- 5.4.3.1 The process of electrolysis Flashcards
(20 cards)
What is Electrolysis?
The process of using electricity to break down a compound into its elements
It only works with ionic compounds because they contain charged ions.
What is an Electrolyte?
Liquids or solutions that conduct electricity
An ionic compound can only be an electrolyte if it is molten or dissolved in water. In solid state, ions are locked and cannot move.
What is a key rule regarding electrolysis?
Electrolysis only works if the ions are free to move.
What happens during electrolysis?
- An electric current passes through the electrolyte.
- Ions move towards the electrodes.
- Ions are discharged at the electrodes, forming elements.
What happens at the cathode during electrolysis?
Positive ions gain electrons and become neutral atoms (Reduction).
What happens at the anode during electrolysis?
Negative ions lose electrons and become neutral atoms or molecules (Oxidation).
What is an example of an electrolyte used in electrolysis?
Molten lead bromide (PbBr₂).
What are the electrodes used in the electrolysis of lead bromide?
Inert electrodes, such as carbon or platinum.
What occurs at the cathode during the electrolysis of lead bromide?
Lead ions (Pb²⁺) gain electrons to become lead metal
Equation: Pb²⁺ + 2e⁻ → Pb
What occurs at the anode during the electrolysis of lead bromide?
Bromide ions (Br⁻) lose electrons to become bromine gas
Equation: 2Br⁻ → Br₂ + 2e⁻
What are the final products of the electrolysis of lead bromide?
Lead metal (Pb) and Bromine gas (Br₂).
What is a half-equation in the context of electrolysis?
Shows what happens at each electrode and balances charges and electrons.
What is the reduction half-equation for lead ions?
Pb²⁺ + 2e⁻ → Pb.
What is the oxidation half-equation for bromide ions?
2Br⁻ → Br₂ + 2e⁻.
True or False: Reduction happens at the cathode.
True.
True or False: Oxidation happens at the cathode.
False.
What are key exam tips for electrolysis?
- Electrolysis only works if the compound is molten or dissolved.
- Positive ions move to the cathode (-), negative ions to the anode (+).
- Ions are discharged at the electrodes and form elements.
Fill in the blank: The cathode always attracts _______.
cations (positive ions).
Fill in the blank: The anode always attracts _______.
anions (negative ions).
What must be done for reactions at the electrodes in higher tier questions?
Write and balance half-equations.
