Electrolysis - Seneca Flashcards
When are charged ions attracted to electrodes during electrolysis ?
When a voltage (direct current) is applied across the electrolyte.
When can electrons be transferred during electrolysis.
When an ion touches an electrode
What is the anode made of to limit price ?
Anode usually made of carbon + good conductor
Disadvantage of electrode - financial
Lots of energy needed to melt the solid ionic compound to allow ions to flow + produce electrical current.
This requires lots of energy - lots of money !
What is another way to test for chlorine ?
Smell of chlorine gas pungent.
How can we observe that a metal is present on the electrode?
Shiny around the cathode
What colour is bromine gas ?
Brown
(Due to high temps reached in the process - gas)
When is hydrogen produced during electrolysis?
When metal higher than hydrogen in the reactivity series.
Where does a HALOGEN form during electrolysis?
Halogen forms at the anode
Half equation for oxygen at the anode
4OH- -> O2 + 2H20 + 4e-
What metals are below hydrogen in the reactivity series?
Copper, silver, gold, platinum
Anode example
Bromine
2Br- -> Br2 + 2e
Cathode example.
Lead
Pb2+ + 2e -> Pb
Copper purification process :
Copper sulfate solution.
Impure copper attached at anode -> copper ions go into electrolyte solution of copper sulfate. Copper ions attracted to cathode and pure copper will form.
When is the reaction complete (copper purification)
When mass of cathode constant
Cathode prep before copper purification
Cathode must be cleaned for copper to stick to it
Why use a variable resistor during electrolysis?
Variable resistor as current may vary - current should be kept constant
Why do we wash the electrodes after electrolysis?
Wash electrode to remove copper sulfate and wash with a more colitle solvent to make them dry faster. E.g. propanone.
What happens to impurities during electrolysis?
Fall to bottom of the beaker
What are concordant results ?
Within 0.1 cm of each other
