changes at the electrodes Flashcards
How do negatively charged ions become neutral atoms?
They lose electrons
How do positively charged ions become neutral atoms?
They gain electrons
What is it called when an ion gains electrons?
Reduction; the ions have been reduced
What is it called when an ion loses electrons?
Oxidation; they ions have been oxidised
How are the changes at each electrode represented?
By using half equations
What happens at the cathode (negative electrode)?
There is reduction of a positive ion
What happens at the anode (positive electrode)?
There is oxidation of a negative ion
What is the half equation for the reduction of lead (Pb^2+)?
Pb^2+ + 2e^- –> Pb
What is the half equation for the oxidation of bromine (Br^-)?
2Br^- –> Br2 + 2e^-
What happens when ions reach an electrode?
They either lose or gain electrons, depending on their charge
Why is electrolysis more complex in aqueous solutions?
Because of the ions formed by water as it ionises (hydrogen and hydroxide ions)
If there are two elements that can be produced at an electrode, which one will be formed?
The less reactive element
What two elements will usually be attracted to the cathode in the electrolysis of solutions?
Positively charged metal ions and H+ ions from water
What happens at the anode in the electrolysis of aqueous solutions?
Hydroxide ions (OH-) from the water are often discharged
What happens when hydroxide ions are discharged?
Oxygen gas is given off at the anode
