electrolysis (required practical) Flashcards
what is electrolysis?
using an electrical current to split ionic compounds into the elements they are made of.
how does electrolysis work?
- an electric current is passed through an electrolyte. a molten or dissolved ionic compound
- ions move towards electrodes where they react and the compound decomposes.
- positive ions move towards the cathode negative electrode and gain electrons. reduced
- negative ions move towards the anode positive electrode and lose electrons. oxidised
- this creates a flow of charge through the electrolyte.
- as ions gain or lose electrons they form the unchanged element and are discharged from the electrolyte.
why are electrodes inert?
so they don’t react with the electrolyte.
when is electrolysis used for ore extraction?
if the metal is more reactive than carbon. can’t be displaced
what ions will always be present in an aqueous solution?
hydrogen ions. H+
hydroxide ions. OH-
what is produced at the cathode if there are hydrogen H+ and metal ions?
hydrogen gas is produced if the metal is more reactive than hydrogen.
what is produced at the anode if hydroxide OH- and halide ions Cl- Br- I- are present?
chlorine bromine or iodine halogens are produced. if no halides are present OH- ions are discharged and oxygen is formed
how do you do electrolysis and identify the products?
- set up a beaker filled with an electrolyte.
- add 2 s-shape electrodes into the beaker and connect them to a power supply.
- place a test tube over each electrode.
- at the cathode you will get pure metal or hydrogen bubbles. gas will be collected in the test tubes
- at the anode you will get oxygen bubbles or halogen bubbles. if a halide is present
now test the gases - hydrogen makes a squeaky pop when lit with a splint.
- oxygen will relight a glowing splint.
- chlorine bleaches damp litmus paper turning it white.
