CHEMISTRY POST LAB HELP PLEASE!!! I don\'t know how to answer this question. The
ID: 1060712 • Letter: C
Question
CHEMISTRY POST LAB HELP PLEASE!!! I don't know how to answer this question. The lab involved determining cell potential that relies on the thermoelectric effect to generate a cell potential called a thermogalvanic cell. These cells don't efficiently convert heat into electrical potential. Any help is appreciated, thank you!!!!
4. Discuss the determined value of cell potential (3.38 x 10^-6) for a thermogalvanic cell in the context of providing practical emf (electromotive force) sources. In other words, could you provide actual sources for emf using this value of cell potential for thermogalvanic cell?
Explanation / Answer
In a thermogalvanic cell, the temperature difference between the elecrodes is the driving force for potential difference generation across the electrodes. It can be understood that in contrast to simple galvanic cells, where concentration gradient diretly creates the flow of ions/electrons and thus the potential difference,a temperature difference cannot create efficient electron flow between electodes, unless we have a very high temperature difference. Because the charged species flow due to a gradient in equillibrium constant of the electrolyte, which itslef depends on temperature.
Thus, the energy efficiency of such thermogalvanic cells is very poor, in the range of 0.1 - 1.0 % for conversion from thermal to electrical energy.
D. The determined value of cell potential is 3.38x10-6 V for the thermogalvanic cell. Practical concentration/electrolytic/electrochemical galvanic cells provide cell potentials of the order of 100 V (0.4 - 4.7V). Suppose we need to power a practical device running on 12V supply. In this case, a battery of around 5 concentration cells can serve the purpose. But if we use the thermogalvanic cells, we will have to use more than 100,000 of those.
Thus, it is not really possible to use thermogalvanic cells for regular needs. However,they prove very useful for utilization of waste heat from thermal power plants, solar cells, solar ponds, etc. , and can sufficiently power microelectronic devices like sensors, processor cores,etc.