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determining cathode from anode
Posted: Fri Mar 16, 2018 9:12 pm
by Abigail Urbina 1K
If we are given two half reactions with their standard cell potentials, how exactly are we supposed to know which is the cathode and which is the anode, and thus which reaction we would need to reverse?
For example on question 3C of the 2014 Final:
Fe3+ + e- --> Fe2+
Zn2+ + 2e- --> Zn(s)
It says that the second reaction is the anode and the first reaction is the cathode. How are we sure of this?
Re: determining cathode from anode
Posted: Fri Mar 16, 2018 9:17 pm
by Michaela Capps 1l
You would look at the standard cell potentials. The most positive is the cathode. Also, cathode-(anode) should be positive.
Re: determining cathode from anode
Posted: Fri Mar 16, 2018 9:21 pm
by Curtis Wong 2D
I am pretty sure that the only way to determine the cathode from the anode is based on their standard cell potential. Cathodes are the ones that are reduced and the the Anodes are the ones that are being oxidized. And we know our Galvanic cell needs to be a positive number so whichever combination of the two leads to the greatest positive cell potential determines the anode and cathode.
Re: determining cathode from anode
Posted: Fri Mar 16, 2018 10:09 pm
by Michael Downs 1L
It is similar to the reducing and oxidizing agents
Re: determining cathode from anode
Posted: Sat Mar 17, 2018 1:58 am
by Rishi Khettry 1L
Calculate cathode - anode substituting both numbers and the combination that gives the most positive output is the correct one
Re: determining cathode from anode
Posted: Sat Mar 17, 2018 8:48 pm
by snehabhargava
Check the standard cell potentials.
Re: determining cathode from anode
Posted: Sat Mar 17, 2018 10:55 pm
by Gwen Peng 1L
The final most likely had a sheet with all of the standard cell potentials which then allows you to determine your anode and cathode. The anode is always the half reaction that has a more positive standard cell potential (higher voltage) because it will be flipped and the sign will become negative, therefore once it is plugged into the equation E standard (cell)= E standard (cathode) - E standard (anode) the double negative will turn into addition.
Re: determining cathode from anode
Posted: Sat Mar 17, 2018 11:48 pm
by Caroline LaPlaca
RED CAT= reduced cathode
Re: determining cathode from anode
Posted: Sun Mar 18, 2018 12:55 am
by Troy Tavangar 1I
The one with the greater cell potential is the cathode.
Re: determining cathode from anode
Posted: Wed Feb 20, 2019 8:15 pm
by Megan_Ervin_1F
Also it is just standard for the anode to appear on the left
Re: determining cathode from anode
Posted: Wed Feb 20, 2019 9:55 pm
by haleyervin7
Megan_Ervin_1F wrote:Also it is just standard for the anode to appear on the left
You can remember this because it is alphabetical from left to right (anode-cathode).
Re: determining cathode from anode
Posted: Wed Feb 20, 2019 10:24 pm
by 805087225
The cathode is where it is reduction, and thus, the potential will be positive(because it is always written in terms of reduction potential) and the other one will be the anode(which causes oxidation to occur - loss of electrons which we can see from the equation given), and thus we know that is the one to reverse.