These calculations are part of the standard college curriculum of the chapter on Electrochemistry but have also been know to show up on a variety of standardized tests as well.
The oxidation state of MnCL2 is used for Mn as +2 and hence the number of electrons are found. In the case of H2O where Hydrogen has an oxidation state of +1 is the number of electrons needed 1 or is it 2 since there are 2 hydrogen atoms?
What if we have a half reaction where 2 moles of the metal are formed at the cathode? Would you just use the 2 moles of metal in the formula or deduce how many electron moles it would take to produce 1 mole of that metal and then plug those values in? Thanks
Hey Cool Kid - it might depend what you are trying to calculate but as you saw in the Manganese example, each Mn requires 2 moles of electrons since it is 2+, and the coloumb is based on moles of electrons so we have to take that into account :)
Great insight. One thing that bothered me, however, is that the professor here made it too easy for lazy students to just memorize a formula to get the answer. He even encouraged it!
I'm not the biggest fan either but a little context. Most of the students in the class have not taken college physics which would make this a much more familiar topic. Current measured in Amps and charge measured in Coulombs are completely new for the majority of students. The second piece of info is that this is often taught as the last thing at the end of a unit often the lecture before an exam so not only is some of the material very unfamiliar, but students have had very little time to learn it before being tested on it. So presenting it conceptually as well as presenting it as a 'plug-and-chug' equation is a sort of compromise. If you watch the entirety of my lectures you'll find that I believe that the best way to master the subject is to thoroughly comprehend it. Happy Studying!
You're welcome! And I don't know if you're familiar with Mark Wiens, but his videos while in Pakistan really show off the people and the food. looks amazing!
Uh oh! My goal is to make the complex simple not the other way around. Can you be specific on where and how you think I made simple stuff complex so I can improve the next time?
