C4.1 - Electrolysis Flashcards
What is electrolysis? [2]
the decomposition of an ionic compound, when molten or in aqueous solution, by the passage of an electric current
What is electrolysis simply? [2]
breaking apart ionic compounds, using electricity
What is an electrode? [3]
- a conductor
- often a metal or graphite rod
- allows electric current to go in or out of an electrolyte
What is an electrolyte? [2]
- the molten or aqueous substance that undergoes electrolysis
What is a cation? [3]
- when an atom loses electrons
- it becomes positively charged
- this is a cation
What is an anion? [3]
- when an atom gains or takes in electrons
- it becomes negatively charged
- this is an anion
What is a cathode? [1]
the negative electrode
What do cathodes attract and why? [2]
- positively charged cations
- because opposite charges attract and since the cathode is negative, it’ll attract positive ions
What is an anode? [1]
the positive electrode
What do anodes attract and why? [2]
- negatively charged anions
- because opposite charges attract and so since the anode is positive, it’ll attract negative ions
How do you remember which electrode attracts which ion? [2]
CAThode –> CATion
ANode –> ANion
What is required during electrolysis? [1]
an electric current to flow through the circuit
What carries the electric charge in an external circuit and where does this happen? [3]
- electrons carry this electric charge
- they carry it from the power supply to the cathode - making it negatively charged
- the anode becomes positively cahrged as it loses electrons
What carries the electric charge in the electrolyte? [1]
the ions carry this electrical charge
What can electrolytes either be? [2]
- a molten compound
- an aqueous solution
What happens when ions touch the electrode? [2]
electrons are either lost or gained, to create neutral substances
What happens to the neutral substances produced after ions touch the electrodes? [1]
they are released as products at the electrodes
What happens at the anode? [1]
anions lose electrons
What happens at the cathode? [1]
cations gain electrons
What is oxidation? [1]
the loss of electrons
What is reduction? [1]
the gain of electrons
What are molten substances? [2]
substances in a liquid state, resulted from being heated above their melting points
What are electrodes made of? [3]
- platinum
- carbon
- graphite
What happens during the electrolysis of molten lead(II) bromide to the ions? [2]
- bromide ions (-) will be attracted to the anode (+)
- lead ions (+) will travel towards the cathode (-)
What are observations seen in the electrolysis of molten lead(II) bromide? [2]
- at the anode, bromine gas is formed which is seen as brown gas bubbles
- at the cathode, lead forms and can be seen as a grey metal (molten lead)
What does aqueous mean? [1]
a substance mixed with water
Where do the ions in the electrolyte come from? [3]
- the dissolved substance
- and water
- which contains hydrogen and hydroxide ions
What is formed at the cathode? [2]
- metals
- or hydrogen
What is formed at the anode? [1]
- non-metals (except hydrogen)
What is the rule for what is discharged at the cathode? [1]
jewellery metal otherwise hydrogen
What are examples of jewellery metals? [4]
- copper
- gold
- silver
- platinum
What is the rule for what is discharged at the anode? [1]
halogen otherwise oxygen
What is the KEY formula for reduction (Hydrogen formula)? [2]
2H⁺ + 2e⁻ –> H₂ (g)
What is the KEY formula for oxidation (Hydroxide formula)? [2]
4OH⁻ –> O₂ + 2H₂O + 4e⁻
What happens during the electrolysis of aqueous copper(II) sulphate using copper electrodes? [2]
- the concentration of Cu²⁺ ions in the electrolytes remains the same
- since one electrode produces copper ions and the other removes them
What is electroplating? [2]
a method used to put a thin layer of a metal onto a metal object, using electrolysis
Why are metal objects electoplated? [2]
- to improve their appearance
- to improve their resistance to corrosion
What is the object that gets electroplated? [1]
the cathode
What is the current flow in an electric circuit for electrolysis and why? [2]
- D.C. current
- because A.C. current would make the direction of the current move many times, hence the electrons wouldn’t be able to follow
Why does the mass of a cathode increase after it has been electroplated? [2]
- because ions go and coat it
- positive ions are attracted to the cathode and make it stronger
What is needed for electroplating? Give an example as well. [2]
- the ions in the solutions of the thing your plating
- e.g. if you’re electroplating gold, you need gold solution
