Electrolysis Flashcards
(36 cards)
How does electrolysis work?
Electrolysis is the decomposition of a compound into the elements that produce it. This only occurs in subsances that conduct electricity.
What is a positively charged ion called? And what is a negative one called?
Cation - positively charged ion
Anion - negatively charged ion
What is the electrode that attracts positively charged ions called?
Cathode
What is the charge of an anode?
Positive
What is the electrode that attracts negatively charged ions called?
anode
What is the charge of a Cathode?
Negative
What is the electode that attracts negative ions called?
anode
How does Cu²⁺ form copper in electrolysis?
(2 points)
- When voltage is applied, the Cu²⁺ ions are attracted to the cathode.
- When they touch the cathode, they gain two electrons to form the copper metal.
What happens at the cathode?
The metal forms
Explain Oxidation and Reduction in terms of electrolysis.
(HINT: OxidAtion, reduCtion)
Oxidation: electrons are lost. This happens at the anode.
Reduction: electrons are gained. This happens at the cathode.
What is an aqueous solution?
A solution where the solvent is water.
What happens at the cathode in the electrolysis of an aqueous solution?
H⁺ (hydrogen) is produced if the metal is more reactive/higher up on the reactivity series than hydrogen.
The metal ions will form if it is less reactive/further down in the reactivity series than hydrogen.
(e.g, copper)
What happens at the anode in the electrolysis of an aqueous solution?
If there are Halide ions present, the respective halides will form.
If there are no halides, oxygen (NOT HYDROXIDE) will form.
What are the half equations for the electrolysis of lead bromide (PbBr₂)?
anode, oxidation:
Pb⁺² + 2e⁻ → Pb
cathode, reduction:
2Br⁻ → Br₂ + 2e⁻
Is the electron a product or a reactant in the half equation or a non metal? And why?
Product. It has an overall negative charge and needs to loose electrons to become stable.
If the electron is a product the substance is gaining electrons.
Is the electron a product or reactant in the half equasion for a metal?
Reactant. It has an overall positive charge and needs to gain electrons to become stable.
If the electron is a reactant the substance is loosing electrons.
What two ions form when water is involved in electrolysis? And what electrode are they attracted to?
Hydrogen ions: Cathode.
Hydroxide ions: Anode.
What is the BALANCED half equation for when oxygen forms at the anode?
4OH⁻ → O₂ + 2H₂O + 4e⁻
Electrolysis can be used to extract copper from a solution of copper (II) sulfate. Suggest how oxygen is also produced.
Oxygen is produced through discharge of hydroxide ions from the water.
State two reasons why we use graphite electrodes in the electrolysis of ionic compounds.
- good conductors of electricity
- inert/unreactive
In the extraction of aluminium from aluminium oxide by electrolysis the positive electrode is made of carbon and needs to be regularly replaced. Explain why.
The oxygen may react with the carbon anode to form carbon dioxide.
How can we test for Hydrogen?
(2 marker)
- squeaky pop test (1 mark)
- a lighted splint is exposed to the hydrogen. If it makes a squeaky pop then hydrogen is present in thr solution (1 mark)
How can we test for oxygen?
(2 marker)
- relight test (1 mark)
- a lighted splint is exposed to the solution. If oxygen is present then the splint will reignite. (1 mark)
Why is the remaining electrolyte an alkali solution after electrolysis has occured in an aqueous solution?
There are excess OH- ions (which are alkali)
