7
$\begingroup$

Primary cells cannot be recharged effectively because their reaction products are not in contact with the electrodes. True or false?

I got it correct just by rote-learning the theory so the answer is true. But when I tried to understand it properly I'm getting confused between a galvanic cell and a primary cell. They both work on the same principles (chemical energy is converted to electrical), but they are not the same thing? Since in galvanic cells are where there are 2 beakers with 2 electrodes, 1 in each, their products are always in contact with electrodes, opposed to primary cells where it is not modelled in the same way (i.e. just a battery where the products can move away from the electrodes)?

$\endgroup$
1
$\begingroup$

Galvanic/electrolyic refers to how the cell is being run. If you have an electrochemical cell, and you connect a load to it, and it produces a spontaneous current, it's a galvanic cell. If instead you connect a voltage source, and the current from the voltage source induces a reaction, it's an electrolytic cell. There's no requirement that a galvanic cell be made with two beakers and a salt bridge, that's just a very common setup for introductory chemistry experiments using the Daniell cell.

The defining characteristic of a secondary battery is that the net "electrolytic" reaction is the reverse of the net "galvanic" reaction. So a secondary battery is a galvanic cell when it's discharging and an electrolytic cell when it's charging. In a primary battery, whatever reaction happens during charge doesn't return the battery to its initial state. A common reason for this is that the galvanic reaction produces insoluble products, so the concentration is really low by the electrode. Then when you reverse the current and run it as an electrolytic cell, something else reacts instead, like water electrolyzing.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.