anode/cathod reversible

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Elizabeth Harty 1A
Posts: 125
Joined: Sat Jul 20, 2019 12:16 am

anode/cathod reversible

Postby Elizabeth Harty 1A » Sun Mar 01, 2020 5:06 pm

Can someone explain how it was known to write the equations in this way when it was written as reversible?
Screen Shot 2020-03-01 at 5.05.43 PM.png

Nicholas Chin 1G
Posts: 100
Joined: Thu Jul 11, 2019 12:17 am

Re: anode/cathod reversible

Postby Nicholas Chin 1G » Sun Mar 01, 2020 5:40 pm

I think because electrochemistry reactions generally only go forward, since they have a positive E(cell) value.

Matthew Chan 1B
Posts: 111
Joined: Sat Sep 07, 2019 12:16 am

Re: anode/cathod reversible

Postby Matthew Chan 1B » Sun Mar 01, 2020 9:33 pm

My guess is, same as Nicholas, that we know that electrochem reactions proceed forward to give a positive Ecell value.

Simon Ketema_1F
Posts: 16
Joined: Wed Nov 13, 2019 12:26 am

Re: anode/cathod reversible

Postby Simon Ketema_1F » Sun Mar 01, 2020 9:40 pm

The reactions in the question are reversible because they are theoretical. But they're asking you to apply those equations in a galvanic cell, and reactions in galvanic cells go to completion. In a different type of question though, you might have to flip one of the reactions so that one is an oxidizing agent and one is a reducing agent. So that might be why they're written as reversible reactions.

Posts: 149
Joined: Thu Jul 25, 2019 12:17 am

Re: anode/cathod reversible

Postby jisulee1C » Sun Mar 01, 2020 9:46 pm

To determine which half reaction is the cathode and anode you have to look at the standard reduction potential. For Co2+ reaction the standard reduction potential is -0.28V and for the Ce4+ reaction the standard reduction potential is +1.61V. Since Ce4+ reaction has a more positive higher voltage it undergoes reduction and is therefore in the cathode which is why it gains electrons in the reaction. You want an overall positive Ecell because it is the reaction in a galvanic cell, spontaneous reaction occurs only with a positive Ecell.

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