SC10 Electrolytic Processes Flashcards
Define cathode
A negative electrode
Define anode
A positive electrode
Define electrode
A rod of metal or graphite through which an electrical current flows in or out of an electrolyte
Define electrolyte
Ionic compound in molten or dissolved solution that conducts the electricity
Define electrolysis
The process in which energy, from a direct current supply, decomposes electrolytes
What ions go towards the cathode?
Cations
What ions go towards the anode?
Anions
What direction do electrons move during electrolysis?
From the power supply to the cathode
What occurs at the anode?
Negative ions lose their electrons
What occurs at the cathode?
Electrons are transferred to the positive ions
What ions will be present in the electrolysis of an aqueous solution?
- The ions of the electrolytes
- OH- ions
- H+ ions
Why are OH- and H+ ions present in aqueous solutions?
Since aqueous substances are those dissolved in water, water will always be present. Those are the ions present in water
What is produced at the cathode of the electrolysis of an aqueous solution?
Hydrogen (from H+ in water) is produced UNLESS the + ions in the ionic compound are from a metal that is less reactive than hydrogen. If the metal is less reactive, it will be produced instead
What are the metals that are less reactive than hydrogen?
- copper
- silver
- gold
- platinum
What is produced at the anode of the electrolysis of an aqueous solution?
Oxygen (from the OH-) and water UNLESS there is a group 7 ion present. If so, then it will be produced
What are the ions present in a molten ionic solution?
The ions of the solution only
What will be produced at the cathode of the electrolysis of a molten solution?
The + ions
What will be produced at the anode of the electrolysis of a molten solution?
The - ions
Why must the electrodes used be inert?
So they don’t participate with the reaction
Define oxidation
The loss of electrons
Define reduction
The gain of electrons
Describe the half equation at the cathode
X+ - e- = X
Where does reduction occur?
At the cathode
Describe the half equation at the anode
X - = X + e-
Where does oxidation occur?
At the anode
What is the anode made of in the formation of copper through the electrolysis of copper sulfate?
Impure copper (that we’re purifying)
What is the cathode made of in the formation of copper through the electrolysis of copper sulfate?
Pure copper
What happens in the formation of copper through the electrolysis of copper sulfate?
- Cu2+ ions from the anode move to the cathode, where they gain electrons and are discharged as pure copper
- impurities form as sludge below the anode
What change occurs in the anode during the electrolysis of copper sulfate?
It loses mass due to the loss of copper ions and impurities
What change occurs in the anode during the electrolysis of copper sulfate?
It gains mass as it gains pure copper
Is there a change in mass of the solution of copper sulfate during its electrolysis?
No, because the loss of mass in the anode is equivalent to the gain of mass of the cathode. Therefore, the concentration of copper ions remains constant
Describe what is produced at the cathode and the anode during the electrolysis of copper chloride solution
Cathode: Copper
Anode: Chlorine
Describe what is produced at the cathode and the anode during the electrolysis of sodium chloride
Cathode: H+
Anode: Chlorine
Describe what is produced at the cathode and the anode during the electrolysis of sodium sulfate
Cathode: H+
Anode: OH-
Describe what is produced at the cathode and the anode during the electrolysis of aqueous sulfuric acid
Cathode: H+
Anode: OH-
Describe what is produced at the cathode and the anode during the electrolysis of molten lead bromide
Cathode: Lead
Anode: Bromine
