Reason For Learning
The displacement reaction between zinc and copper ions, demonstrates that zinc is a better reductant than copper and would therefore be oxidised more readily than copper. As zinc is oxidised, elec-trons ?ow from the zinc metal to the copper ions.
Zn(s) + Cu2+(aq) Zn2+(aq) + Cu(s)
This is a spontaneous reaction and requires no energy; in fact, it releases energy. Energy may be released in a number of forms such as heat, light, electricity or sound. The set-up of the displacement reaction determines the form of energy that is released. For example, when zinc metal is placed in direct contact with copper ions, all the chemical energy of the reaction is released as thermal energy (heat) and the transfer of electrons from zinc to copper ions occurs on the surface of the zinc metal.
The energy generated by such reactions can be used, and this is the basis for batteries.
Learning Intention
After completing this learning bite you should know:
Chemical energy can be converted into electrical energy. Solutions that are able to conduct a current are known as electrolytes. The electrode at which oxidation occurs is called the anode, and it has a negative charge. The electrode at which reduction occurs is called the cathode, and it has a positive charge. All of these components together are known as an electrochemical cell.
A simple electrochemical cell consists of:• two half-cells, containing two electrodes (anode and cathode) and two electrolytes
• a conducting wire
• a salt bridge, containing another electrolyte.
Key Vocabulary Terms