Standard hydrogen electrode (the reference electrode) - A half-cell in which hydrogen gas at a pressure of one atmosphere bubbles into a solution of 1M H+ ions.
The standard electrode potential of a half cell is measured by making a cell with a 'standard hydrogen electrode' This is used as a reference electrode so has an electrode potential of 0V Another half-cell is essential for this measurement to be made. Measuring the standard electrode potential for a Zn2+/Zn half-cell Measuring Standard electrode potentials E O Įlectrode potential - The voltage measured for a half-cell. With this reaction always work out the difference and don't worry about minus signs. The voltage of the cell can be calculated from the difference in the electrode potentials e.g. Therefore, the copper half-cell is higher and the zinc reaction is in reverse. The voltage for the reduction of copper 2+ ions is +0.34V and for the reduction of Zinc 2+ ions is -0.76V. In a cell, the higher electrode potential half-cell will undergo the forward reaction and the lower the reverse. The more 'easily' the reduction reactions happen (as above in the half-equations) the higher the electrode potential value in volts. One half-cell supplies electrons, the other half-cell receives electrons copper half-cell If we set up this reaction as an electrochemical cell we can measure the voltage of the reaction in the cell.Īn electrochemical cell is an exothermic reaction set up as two half-cells in two separate containers so that the energy released can produce current between themĪ half-cell is half of an electrochemical cell. 3 What standard electrode potentials meanĮlectrode potentials īut as you may notice the second reaction must occur in reverse for the redox reaction to happen and for zinc to be oxidised (loss of electrons).2 Measuring Standard electrode potentials E O.
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