Electrolysis Flashcards
What is electrolysis?
Using electricity to break down an ionic compound into elements
Why must ionic compounds be liquid or dissolved in water for electrolysis to work?
So ions can move and carry charge
Explain what happens at the cathode (negative electrode)
Positive ions (cations) are attracted and gain electrons in reduction
Explain what happens at the anode (positive electrode)
Negative ions (anions) are attracted and lose electrons in oxidation
At which electrode would Zn2+ turn into Zn?
Negative electrode
At which electrode would Cl- turn into Cl2?
Positive electrode
Complete the half equation: Al3+ + ___ —> ___
Al3+ + 3e- —> Al
Complete the half equation: Cl- —> ___ + ___
2Cl- —> Cl2 + 2e-
Complete the half equation: ___O2- —> ___ + ___
2O2- —> O2 + 4e-
What will be the products for the electrolysis of molten iron bromine?
Iron and bromine
What will be the products for the electrolysis of molten zinc oxide?
Zinc and oxygen
What is the disadvantages of using electrolysis?
Requires a large amount of electrical energy which is expensive
Why is aluminium oxide mixed with cryolite when extracting aluminium?
To lower the melting point
What is produced at the anode and cathode in the electrolysis of aluminium oxide?
Aluminium at the cathode and oxygen at the anode
Why does the anode need to be replaced in the electrolysis of aluminium oxide?
The oxygen reacts with the carbon electrode to produe carbon dioxide
Where does hydrogen come from in electrolysis of solutions?
Water
Where does oxygen come from in electrolysis of solutions?
Hydroxide ions from water
When is hydrogen made at the negative electrode in solutions?
If the metal is more reactive than hydrogen
When is oxygen made at the positive electrode in solutions?
If the non-metal ion is not a halide
Which two ions are involved in electrolysis when water is present?
H+ ions and OH- ions
In the electrolysis of sodium chloride solution, what are the products?
Chlorine gas, hydrogen gas and sodium hydroxide
In the electrolysis of sodium chloride solution, why is hydrogen gas produced?
Sodium is more reactive than hydrogen
In the electrolysis of sodium chloride solution, why is chlorine gas produced?
Chloride is a halide ion
In the electrolysis of sodium chloride solution, why is sodium hydroxide produced?
Left over sodium ions and hydroxide ions remain in the water
