Electrolysis Flashcards
Why do solid ionic compounds do not conduct electricity but molten or dissolved ionic compounds do?
Ions cannot move in solid.
Ions can move when molten or dissolved.
What is an electrolyte?
A molten or dissolved ionic compound that decomposes when it conducts electricity.
Define oxidation and reduction
OIL RIG
Oxidation is the loss of electrons
Reduction is the gain of electrons
What is formed at the anode and cathode when a molten ionic compound conducts electricity?
Anode- non metal forms
Cathode- metal forms
What are the possible products at the anode and cathode when a solution conducts electricity?
Anode- halogen or oxygen ( from the water )
Cathode- metal or hydrogen (from the water)
Which ions are attracted to the positive electrode(anode)?
Negative ions
Which ions are attracted to the negative electrode(cathode)?
Positive ions
What is brine?
Concentrated sodium chloride solution.
What is formed at the cathode when brine undergoes electrolysis?
Hydrogen
What is formed at the anode when brine undergoes electrolysis?
Chlorine
What is left in solution when brine undergoes electrolysis?
Sodium hydroxide solution
Give a use of chlorine
Killing bacteria in drinking water, swimming pools , or making bleach
Give a use or hydrogen
Making margarine or as a rocket fuel
Give a use of sodium hydroxide
Making bleach and soap
Which 4 ions are in sodium chloride solution?
Na+
OH-
H+
Cl-
Electrolysis of brine: give the half equation at the anode
2Cl- –> Cl2 + 2e
Electrolysis of brine: give the half equation at the cathode
2H+ + 2e- –> H2
What is bauxite and what compound does it mainly contain?
An ore that contains aluminium oxide
Extraction of aluminium: why is cryolite used?
To lower the melting point so less energy is needed
Extraction of aluminium: why do the anodes have to be replaced regularly?
The oxygen produced reacts with carbon anodes to produce carbon dioxide so they burn away.
Extraction of aluminium : what is missing from this half equation?
Al3+ + _____ –> Al
3e-
Extraction of aluminium: what is missing from this half equation?
2O2- -> O2 + ______
4e-
Extraction of aluminium: what is produced at the anode and cathode?
Anode- oxygen
Cathode- aluminium
Electrolysis of MOLTEN SODIUM CHLORIDE: what is produced at the anode and cathode?
Anode- chlorine
Cathode- sodium
Electrolysis of copper chloride solution: what is produced at the anode and cathode?
Anode- chlorine
Cathode- copper
Electrolysis of copper sulphate solution: what is produced at anode and the cathode?
Anode- oxygen
Cathode- copper
Which substance produces zinc at the cathode and chlorine at the anode?
Molten zinc chloride
Define electrolysis
The process that uses electricity to break down ionic compounds into elements.
The substance that breaks down is called the…?
Electrolyte
What must be done to ionic compounds before they can be electrolysed?
It must be dissolved or melted
What are the electrodes made from?
An inert substance that does not react with the products
Fill in the gap:
The ions in the electrolyte move to the electrodes where they are discharged to produce ________
Elements
Fill in the gaps:
Positively charged _______ are attracted to the _________ electrode where they form ________ or _________.
Ions
Negative
Metals or hydrogen
Fill in the gaps:
Negatively charged ________ are attracted to the _________ electrode where they lose their charge to form non- metallic elements.
Ions
Positive
An ion always moves to the ?
Oppositely charged electrode
Fill in the gaps:
When positively charged ions reach the ________ electrode they ________ electrons to become neutral atoms.
This is called?
Negative
Gain
Reduction
At the positive electrode, negative ions ______ electrons to become neutral atoms.
This is called?
Lose
Oxidation
What’s the half equation at the anode for lead bromide?
2Br–> Br2 + 2e-
What’s the half equation at the cathode for lead bromide?
Pb2+ + 2e- –> Pb
How is aluminium manufactured?
Aluminium oxide is electrolysed
What forms at the cathode and anode during the extraction of Aluminium?
Anode- oxygen
Cathode - aluminium
What products do we get when we electrolyse brine?
Chlorine gas, hydrogen gas, sodium hydroxide solution
Why is hydrogen produced when sodium chloride is electrolysed?
The solution contains hydrogen ions which are discharged in preference to sodium ions because sodium is more reactive than hydrogen.
Why is the electrolysis of brine an important industrial process?
It’s three products have many uses
Why can we electroplated objects?
To improve their appearance , protect their surface, and use smaller amounts of precious metals.
Why,are some knives, forks and spoons silver plated?
To make them look attractive, to protect the metal from corrosion and to reduce costs.
