C6 - Electroylsis - Complete Flashcards
What type of compound can be broken down by electrolysis?
An ionic compound
What is the electrolyte of an electrolysis reaction?
The ionic compound being separated
What is an electrode?
A conducting rod connected to a specific terminal from the power supply
Which is the positive electrode?
The anode
Which is the negative electrode?
The cathode
What are the electrodes made of and why?
Unreactive substances such as graphite or platinum, so that they do not interfere with the separation process by reacting with the compound or separating themselves
What happens during electrolysis?
The positive ions move to the negative and the inverse to the inverse, as opposite charges attract. At the electrodes, the ions lose their charges and become elements. Often a chemical will be deposited or a gas released, depending on the compound used and whether it was molten or dissolved in water
Why are the compounds often dissolved in water or molten?
As when they are solid they cannot conduct electricity as their ions are fixed in a large lattice structure
What does electrolysis do?
It breaks down a substance using electricity
What is a setback of dissolving an ionic compound in water for electrolysis?
It can be hard to predict what will be formed at each of the electrodes, and in what form the products will be
What happens when ions reach an electrode?
They either lose or gain electrons based on their charge
What is the gaining of electrons called?
Reduction (Think OILRIG)
What is the loss of electrons called?
Oxidation (Think OILRIG)
What is the best way to display the reactions going on at each electrode?
Half equations that demonstrate the movements and charges of the particles (e.g. Pb + e- —> Pb-)
What ions does water form when it ionises?
Hydrogen (H+) ions and Hydroxide (HO-) ions, both aqueous (aq)
Out of more and less reactive ions, which is more likely to form at the electrode?
The less reactive one
What is the order of most likely to be discharged at the anode to least likely?
Halide ions > Hydroxides > All other negatively charged ions
What are 3 uses of aluminium or its alloys?
Pans / Overhead power cables / Aeroplanes / Cooking foil / Drink cans / Window and patio door frames / Bicycle frames and car bodies
Why can’t aluminium be separated using any other method than electrolysis?
As it is too reactive to be displaced by carbon, is less reactive than magnesium but more so than iron and zinc
What is the compound used to separate aluminium in electrolysis?
Al2O3
What is the raw form of aluminium that can be extracted from the ground?
Bauxite ore, which is mainly aluminium, but also contains many rocky impurities such as Iron (III)
Why is molten cryolite mixed with aluminium in electrolysis?
To lower aluminium’s high boiling point so that its extraction is more sustainable and consumes less energy
Why do the carbon anodes used in aluminium purification have to be replaced?
As the oxygen that forms there often reacts with the carbon to make carbon dioxide: meaning that they end up wearing away over time
What three useful products does the electrolysis of brine produce?
Chlorine gas at the anode, hydrogen gas at the cathode, and sodium hydroxide solution
