AP Electrochemistry – what do you need to know…
The formula list that is part of your AP packet is here:
Yep, that’s it!
Depending on the equation sheet to help you out in an exam is never the best idea. Do memorize these equations. You do need to know the following:
- How to recognize an oxidation or reduction equation and how to write the half reactions.
- How to balance a redox reaction.
- What a Galvanic vs. Electrolytic cell is and all the parts therein.
- Be able to identify a cathode and anode in either of the above cells.
- Understand the processes that happen in the cathode, anode, salt bridge, etc.
- Calculate the cell potential, E, and understand what it means wrt spontaneity.
- Remember that ΔG also relates to the equilibrium constant K.
- Now we have 3 parallel measures of spontaneity. K, ΔG and E.
- K>1, ΔG<0 and E>0 for a spontaneous process.
In an electrolytic (non spontaneous) cell, you will be often asked to find the amount of metal deposited when a current (I) is run through the cell for a certain amount of time. You then go through the following process:
I (current)→q (charge)→molese→molesmetal→gramsmetal or the other way, as the question may be.
- I → q. This is what the equation on your sheet is for:
- q/F = ne, the number of moles of electrons you have used. F here is the faraday’s constant, also in your equation sheet.
- Use your reduction equation here, eg. Al3+ + 3 e–→ Al. This shows a 3:1 molar ratio between ne and nmetal
- Find nmetal using this ratio
- Multiply by molar mass to find grams of the metal!