electrolysis Flashcards
definition of electrolysis
using electricity to split ionic compounds
main uses of electrolysis
-extraction of metals
-make chlorine gas
-make hydrogen gas
-making soap
why must the compound be molten or dissolved?
These compounds are called electrolytes. The ions are free to move/ carry charge, therefore they can conduct electricity.
What happens at the electrodes?
Ions are DISCHARGED, turning into uncharged ions.
What must happen for an anion (negative electron) to be discharged?
The anion must LOOSE electrons = oxidation
What must happen for a cation (positive electron) to be discharged?
The cation must GAIN electrons = reduction
Which ion is attracted to the anode?
The ANION is attracted to the anode, the POSITIVE electrode
Which ion is attracted to the cathode?
The CATION is attracted to the cathode, the NEGATIVE electrode.
Why are these ions attracted to these electrodes?
Because opposite charges attract!
Why is there a cell and bulb in the circuit?
Cell- source of electrical current
Bulb- confirms electrical conductivity throughout circuit.
When electrolysing magnesium chloride, positive Mg2+ ions attract to the cathode. What process takes place and why and what is deposited?
-Reduction takes place
-a solid metal deposits, forming around the cathode.
-because magnesium is a metal
When electrolysing magnesium chloride, negative Cl- ions attract to the anode. What process takes place and why and what is deposited?
-Oxidation takes place
-this must happen to TWO Cl- ions as halogens must form diatomic molecules
-as Cl2 is a gas, we will see effervescence around the anode
Half equation for magnesium
Mg2+ + 2e- = Mg
Half equation for chlorine
Cl2 + 2e- = 2Cl-
Half equation for sodium
Na+ + e- = Na
Half equation for bromine
Br2 + 2e- = 2Br-
Half equation for zinc
Zn2+ + 2e- = Zn
Half equation for hydrogen
2H+ + 2e- = H2
Half equation for hydroxide
4OH- = 2H2O + O2 + 4e-
What is the electrolyte?
The substance broken down that is electrically conductive.
What’s the advantage of aqueous over molten?
It uses less energy, however we get different products
During aqueous electrolysis, there are always what present?
-Hydrogen ions (H+)
-Hydroxide ions (OH-)
Why are these ions present in aqueous electrolysis?
Because the water splits under the current
Aqueous electrolysis - Cathode
The positive cation that will form the ??? reactive product is discharged. If a metal, ???. If hydrogen, then ???
-Least reactive
-If a metal, then solid metal will deposit
-If hydrogen, then hydrogen gas will effervescence
