Urgent help chemistry electrode potentials

Hi, plz help with this question the correct answer is given. I don’t understand why the cell potential is (0) least positive minus (+0.34) most positive.
The rule to calculate cell potential is most positive minus least positive. So why is it the opposite in this question? Also I don’t understand how you determine if H+ is or isn’t a powerful enough oxidising agent.

Also the same about this question below I don’t understand:

(edited 1 year ago)

Reply 1

username5508464

9

Yea not sure why they swap it around thought it's Reduction - Oxidation so 0.34-0=0.34V since the more positive one is reduction. Same for the other board. Also I think it doesn't react as Copper is below hydrogen in the reactivity series, so it can't displace it.

We haven't actually started this topic yet so I'm not too sure on it! :confused:

(edited 1 year ago)

Reply 2

Alevelhelp.1

OP

15

Original post by Buddy564

Yea not sure why they swap it around thought it's Reduction - Oxidation so 0.34-0=0.34V since the more positive one is reduction. Same for the other board. Also I think it doesn't react as Copper is below hydrogen in the reactivity series, so it can't displace it.

We haven't actually started this topic yet so I'm not too sure on it! :confused:

Which exam board r u doing?

Reply 3

username5508464

9

Original post by Alevelhelp.1

Which exam board r u doing?

ocr

Reply 4

ghostyblop

8

Original post by Alevelhelp.1

Hi, plz help with this question the correct answer is given. I don’t understand why the cell potential is (0) least positive minus (+0.34) most positive.
The rule to calculate cell potential is most positive minus least positive. So why is it the opposite in this question? Also I don’t understand how you determine if H+ is or isn’t a powerful enough oxidising agent.

Also the same about this question below I don’t understand:

Cell potential= reduction- oxidation

OIL RIG

Hydrogen is reduced as it's gaining electrons
Copper is oxidised as it's losing electrons

So E0=0-0.34= -0.34V

(edited 1 year ago)

Reply 5

username5508464

9

Original post by ghostyblop

Cell potential= reduction- oxidation

OIL RIG

Hydrogen is reduced as it's gaining electrons
Copper is oxidised as it's losing electrons

So E0=0-0.34= -0.34V

Oh did u get that from the arrows? Cu arrow right to left so its oxidised, hydrogen left to right so reduced?

Reply 6

Alevelhelp.1

OP

15

Original post by ghostyblop

Cell potential= reduction- oxidation

OIL RIG

Hydrogen is reduced as it's gaining electrons
Copper is oxidised as it's losing electrons

So E0=0-0.34= -0.34V

Thanks but what about the arrows, according to the rules more positive goes from left to right and +0.34v is more +ve than 0 but the arrow goes from right to left plz explain

Reply 7

ghostyblop

8

Original post by Buddy564

Oh did u get that from the arrows? Cu arrow right to left so its oxidised, hydrogen left to right so reduced?

Original post by Alevelhelp.1

Thanks but what about the arrows, according to the rules more positive goes from left to right and +0.34v is more +ve than 0 but the arrow goes from right to left plz explain

I think you need to consider that this is a metal + acid reaction where Metal + Acid ---> Metal Salt + H2

ie H+---> H2 and Cu---> Cu2+ otherwise this reaction wouldn't make sense, so the H+ must be reduced and Cu must be oxidised. This would make sense considering the given answer above.

In terms of the second question you're asked if Chlorine will oxidise manganese ions, if chlorine is the oxidant it is being reduced hence why
the calculation is 1.36-1.51= -0.15V

Hope this is helpful lemme know if you have more q's :smile:

(edited 1 year ago)

Reply 8

milliex_grace1

9

Original post by Alevelhelp.1

Hi, plz help with this question the correct answer is given. I don’t understand why the cell potential is (0) least positive minus (+0.34) most positive.
The rule to calculate cell potential is most positive minus least positive. So why is it the opposite in this question? Also I don’t understand how you determine if H+ is or isn’t a powerful enough oxidising agent.

Also the same about this question below I don’t understand:

Hi, I don't know if you're still confused about this but the arrows on both these photos are wrong.

If you made a basic number line of the V values, the more positive value would be on the right. (pretty obvious).
And the species being reduced always goes on the right.

Reduction = gaining electrons so for both whiteboards the arrows need to be the other way round.

This means when you do reduction - oxidation it should make sense now :smile:

(edited 1 year ago)

Urgent help chemistry electrode potentials

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