Flashcards in Electrolysis Deck (39):
Explain what is electrolysis
If you pass on electric current through an ionic substance thats molten or in a solution it breaks down into the elements it's made of this is electrolysis
What does electrolysis require to conduct electricity?
It requires a liquid to conduct electricity called the electrolyte
What do electrolytes contain?
Electrolytes contain free ions . They are usually the molten or dissolved ionic substance
What happens during electrolysis?
Electrons are taken away from ions at the positive electrode and given to other are ions at the negative electrode
What does electrolysis reactions involve?
What is reduction?
Reduction is the gain of electrons
What is oxidation?
Oxidation is the loss of electrons
What does OIL RIG stand for
When will a salt conduct electricity?
When it is molten
What does electrolysis mean?
Electrolysis is the splitting up with electricity
When common salt is dissolved in water and electrolysed what three useful products are made?
Hydrogen , chlorine and sodium hydroxide
What is the name of the positive and the negative electrodes?
Positive - anode
Negative - cathode
At which electrode do ions lose electrons through oxidation?
At which electrode do ions gain electrons through reduction?
What are the two useful products of the electrolysis of sodium chloride solution used in industry?
1) chlorine has many uses such as bleach and plastics
2) sodium hydroxide is a very strong alkali which is used in the chemical industry such as to make soap
How is electrolysis used with aluminium?
Electrolysis is used to remove aluminium from its ore
What is aluminium is ore called?
What is cryolite used to do?
Cryolite is used to lower the temperature (and costs)
What is aluminium and cryolite used to do together and why?
Aluminium oxide is dissolved in molten cryolite because aluminium oxide has a very high melting point of over 2000°C which would be very expensive to melt
Which electrodes are aluminium and oxygen formed at?
Aluminium forms at the negative electrode is an oxygen forms at the positive electrode
What does it mean when oxygen reacts with carbon in the electrode to produce carbon dioxide ?
This means that the positive electrode is gradually getting away and has to be replaced every now and again
What is electroplating?
Electroplating coats one metal onto the surface of another
When electroplating which electrode do you put the metal object you want to plate and the pure metal you want it to be played with
The negative electrode is the metal object you want to plate
The positive electrode is the pure metal you want it to be plated with
How would you electroplate silver onto a Brass cup?
You would make the brass cup of the negative electrode (to attract the positive silver ions). Then you would make a lump of silver the positive electrode. Then you would dip them in a solution of silver ions (e.g silver nitrate)
What are the two different uses for electroplating?
In electroplating how is decoration a useful property?
Silver is attractive but expensive.
It's much cheaper to plate a brass cup with silver than it is to make the cup out of solid silver but it looks just as pretty
How is conduction a useful property for electroplating?
Metals like copper conduct electricity well . Because of this they're often used to plate metals for electronic circuits and computers.
What state must an ionic compound be in if it's to be used as an electrolyte?
It must be molten or dissolved in water
In electrolysis what is meant by the terms oxidation and reduction
Oxidation is loss of electrons and reduction is the gain of electrons
At which electrode are metals deposited during electrolysis?
At the negative electrode
During the electrolysis of molten lead bromide, which gas is produced at the positive electrode?
An object requires electroplating. Which electrode should it be used as?
The negative electrode
During electrolysis what is the name of the gas produced at the negative electrode?
State the half equation for the reaction of the negative electrode when hydrogen is produced...
2H+ + 2e- --> H2
What is the name of the gas produced at the positive electrode during electrolysis of a sodium chlorine solution?
Suggest one use for the gas produced at the positive electrode (chlorine)
The production of bleach or plastic bags
Explain why aluminium oxide is dissolved in molten cryolite (2)
To lower the temperature that electrolysis can take place at. This makes it cheaper
Explain why sodium hydroxide is left in the solution at the end of the reaction (3)
Sodium is more reactive than hydrogen, so sodium ions stay in solution. Hydroxide ions from water are also left behind. This means that sodium hydroxide is left in the solution.