Galvanic cells, such as the Daniell cell below, feature a lot in Chemistry books. For one of my Chemistry EEIs I decided to look at the effect of the temperature and concentration of the solutions on the voltage produced.
I used a simple Daniell cell, which required: zinc sulphate, copper sulphate (both readily available from Bunnings, around $12 to $13 for 500g), a zinc and a copper electrode (zinc plated nail would do), some sodium sulphate (which I created by reacting copper sulphate with sodium bicarbonate) and a voltmeter. I also used an electric frying pan to heat up the beakers containing the solutions.
Standard electrode potentials are always specified as the voltage potential under standard conditions (25°C, 1.00 mol L-1), as the voltage is dependent upon both temperature and electrolyte concentration. Here, the effect of temperature and concentration on the voltage of a Daniell cell is quantified. The results were quite dissimilar to that of previous work in this area; this may be due to differences in the salt bridge used. At a constant temperature of 30°C, the electrolyte concentration had a moderate effect on voltage potential – up to 1.3%. The relationship between voltage and temperature was dependent upon the electrolyte concentrations, however all trials showed a strong positive correlation. The maximum change in voltage potential observed was 1.95%, when the temperature of the cell changed from 24 to 69°C. These results may be of importance to manufacturers of batteries or electronic devices that might be used in extreme temperatures.
The graph below shows the basic result.
The full (12 page) report is available here. This was a fantastic investigation, and many questions remain, such as why the results did not follow the predictions from the Nernst equation.