electrolysis part 2

reactivity series

Potassium

Sodium

Calcium

Magnesium

Aluminium

Carbon
Zinc

Iron

Tin

Hydrogen

Copper

Silver

Gold

more reactive metals are

• strongest reducing agent , loses electrons readily + oxidised

• more reactive metal reduces the ions of / can displace a less reactive metal

voltaic cell

• serves like a battery, converts chemical energy to electrical energy

• in a voltaic cell, the electrical energy is produced from a spontaneous redox reaction in which electrons are transferred through an external circuit

a simple voltaic cell consists of

2 electrodes made of metals with different reactivities , immersed in an aqueous electrolyte solution

• solution should contain ions of less reactive metal

what is at the anode

• the metal higher in reactivity series as it is oxidised and loses electrons to form positive ions

How does electrons flow in the voltmeter

electrons flow through the external circuit (wire) to the less reactive metal at the cathode (from more reactive to less reactive)

what is at the cathode

• the lower in reactivity series metal acts as the cathode

• At the cathode, positive ions in the electrolyte gain electrons and are reduced to form neutral atoms

the farther apart 2 metals are in the reactivity series

the greater the cell voltage

• eg zinc-copper cell : cell voltage of 1.1V but magnesium and copper 2.7V because they are further apart in reactivity diagram so their voltage is larger

• further apart=larger voltage

example of zinc electrode and copper electrode with aqueous CuSO₄

example of zinc electrode and copper electrode with aqueous H₂SO₄