Which Electrode is the Cathode in an Electrochemical Cell?

[Mozart]

Hello everyone. I am having trouble with a question on electrochemical cells.
I have to find the balanced REDOX reaction of the cell. All I am given is a diagram with the following information

1. Aluminum electrode submerged in 1 mol/L Aluminum Nitrate Al(NO3)3(aq)

2. Nickel electrode submerged in 1 mol/L Nickel Nitrate Ni(NO3)2(aq)

3.There is a salt bridge KNO3(aq)

With this information I stall because I can't figure out which one is the cathode, and which one is the anode. I know that NO3 is a polyatomic ion with a charge of -1 so that would make Al+3, and Ni+2. How do I figure out which one is being oxidized, and which one is being reduced? If I knew that then I would be able to balance the reaction. Please help me I tried many things, and can't figure it out. My notes don't tell me either so I am guessing its common knowledge that I missed out on.

 

[Gokul43201]

Google "standard reduction potential". The species with a lower (more negative) reduction potential will get reduced. Oxidation happens at the other electrode.

 

[Mozart]

I tried using what you said and arrived at the wrong answer. So I googled standard reduction potential, and electrochemistry and I found the opposite of what you said. Here is an excerpt "The oxidizing agent that has the more positive reduction potential will be more preferentially reduced and therefore will be the stronest oxidizing agent."
I arrived at the right answer after keeping this in mind. Maybe I am reading what you wrote the wrong way.

 

[F|234K]

mozart you are right, the ones which have the highest reduction potential will get reduced, and the one that have the highest oxidation potential (or lowest reduction potential) will get oxidized.

you should have a chart full of all the redox reactions to do this question. and i think your teacher should have went over a similar problem when teaching, beacuse its not a trick question.

 

[Gokul43201]

Oops, my bad ! Got that backwards, didn't I ? Sorry for the screw up.

Yes, the electrode with the greater (more positive, or less negative) reduction potential will get reduced.