Electrochemistry Flashcards
what is an electrolyte
a substance that condducts electricity when dissolved in water or molten
Under what two circumstances in which ionic compounds can conduct electricity/ act as electrolytes
If dissolved in water/ solution
If molten
how can an electric current be conducted through an electrolyte
ions are avlailable and free to move
what is electrolysis
the passing of electricity through an electrolyte to cause a chemical reaction
what is an electrode
a solid material that conducts electricity
what occours at the cathode
reduction
what occours at the anode
oxidation
decribe the obervations seen ( using green copper (II) chromate solutions)
Demostrating the movement of ions when connected to a electrical current
Observation: a yellow colour will migrate towards the anode and a blue colour will migrate towards the cathode.
The yellow colour caused by the chromate ions.
The blue colour is caused by the copper (II) ions
Inert electrodes reaction
electrodes do not react with the electroyte in which they are placed
Active electrodes reactions
electrodes that react with the electroyte in which they are placed
Inert electrodes suitable to use for these electrolysis
Platinum
Graphite (Carbon)
Active electrodes suitable to use for these electrolysis
Copper electrodes
H2O will always reduce before the following ions
So4 2-
Na+
K+
what was the result/ Observation
Electrolysis of acidified water (H2o + H+) using inert electrodes
- Bubbles of Hydrogen gas will collect over the cathode
- Bubbles of oxygen gas will collect over the anode
the volume of hydrogen will always be double the amount of oxygen formed ( 1 mole of hydrgen formed for every half mole oxygen formed)
Balanced chemical equation for reaction at cathode
Electrolysis of acidified water (H2o + H+) using inert electrodes
2H+ + 2e- → H2↑
balanced chemical equation for reaction at anode
Electrolysis of acidified water (H2o + H+) using inert electrodes
H2O - 2e- → 2H+ + 1/2O2↑
Describe the reacrion/ result
Electrolysis of sodium sulfate (NaSO4) using inert electrodes
- Bubbles of hydrogen gas will collect over the cathode.
- The universal indicator turns from green to blue at the cathode.
- Bubbles of oxygen gas collect over the anode.
The universal indicator turns from green to red at the cathode
the volume of hydrogen will always be double the amount of oxygen formed ( 1 mole of hydrgen formed for every half mole oxygen formed)
Balaced chemical equation describing the reaction at the Cathode
Electrolysis of sodium sulfate (NaSO4) using inert electrodes
2H2O - 2e- → H2↑ + 2OH-
Balaced chemical equation describing the reaction at the anode
Electrolysis of sodium sulfate (NaSO4) using inert electrodes
H2O - 2e- → 2H+ + 1/2O2↑
list the reactions and obervations
Electrolysis of potassium iodide (KI) solution using inert electrodes
Bubbles of Hydrogen gas will collect over the cathode
Phenolphthalein turns from colourless to pink at the cathode
A red-brown colour will form at the anode due to the formation of iodine (I2)
Write a balanced equation for the reaction that occours at the cathode
Electrolysis of potassium iodide (KI) solution using inert electrodes
2H2O - 2e- → H2↑ + 2OH-
Write a balanced equation for the reaction that occours at the anode
Electrolysis of potassium iodide (KI) solution using inert electrodes
2I- - 2e- → I2
Describe the result/ observation
Electrolysis of aqueous copper sulfate (CUSO4) using active electrodes
- The pure copper cathode increases in mass as the Cu 2+ ions in solution are reduced to Cu
- The impure copper anode is ‘eaten away’ and decreases in mass and the cu atoms in the anode are ocidised to CU 2+
Impurities are undissolved and fall to the bottom of the beaker under the anode
describe the reaction at the cathode
Electrolysis of aqueous copper sulfate (CUSO4) using active electrodes
Cu 2+ +2e- → Cu↓
