A short introduction to the Daniell cell

figures 16.5 and 16.6 show the Daniel cell which is one of the simplest electrochemical cells you'll meet you need to have good understanding of what the different parts of the cell do before you go on to more complex cells we look at the diagrammatic representation here like all electrochemical cells there are two half cells an oxidation occurs at one in this case the ZN zn2+ half cell and reduction occurs at the other the CU cu2+ half cell when current is drawn from the cell ZN is oxidized to zn2+ and electrons flow down the wire to the right hand half cell where cu2+ is reduced to CU but why the salt bridge one way of thinking about it is that it completes the circuit but if that's all you might think that piece of wire would do but of course it would here's the explanation as current is drawn from the cell zn2+ ions build up in the left hand half cell and this leads to buildup of positive charge in the right hand half cell cu2+ ions are removed and this means buildup of negative charge say from the sulfate ions if the solution is copper sulfate so there's buildup of positive charge charge on the left and negative charge on the right and without the salt bridge this would prevent any current flowing what the salt bridge does is to provide path for negative ions to flow towards the leftand half cell to counteract the buildup of positive charge and positive ions to flow towards the right hand electrode to counteract the buildup of negative charge the salt bridge is tube containing solution of an electrolyte the electrolyte could also be held in something else like strip of absorbent paper it doesn't matter much what the electrolyte is provided it doesn't react with the Solutions in the half cells sodium sulfate or potassium chloride are often used the Daniel cell is very simple but this basic setup half cells with oxidation and reduction joined by salt bridge is common to most of the other electrochemical cells that you'll meet