Aqueous electrolysis

Ions in water

H+ and OH-

H+ is attracted to

Cathode

Discharge of H+

2H+ +2e → H2

OH- is attracted to

Anode

Discharge of OH-

4OH- → O2 + 2H2O + 4e-

Discharged at the cathode in solution

Least reactive element

Discharged at the anode in solution

Halide ions, if present, otherwise OH

Halide ion

a negative ion formed from a group 7 element

Test for hydrogen

Lit splint produces a squeaky pop

Metals discharged in preference to hydrogen

Copper, Silver, Gold, Platinum

Test for chlorine

Bleaches damp litmus paper

Test for oxygen

Relights a glowing splint