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Author Topic: EMF  (Read 2715 times)

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sharonjh

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EMF
« on: September 11, 2010, 12:59:44 AM »

 Consider an electrochemical cell with the following cell reaction where all reactants and products are at standard-state conditions.
Cu2+ (aq) + H2(g) ® Cu(s) + 2H+(aq)
Predict the effect on the emf of this cell of adding NaOH solution to the hydrogen half-cell until the pH equals 7.0.

   The emf will increase.
   The emf will decrease.
   No change in the emf will be observed.
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MrTeo

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Re: EMF
« Reply #1 on: September 11, 2010, 01:45:13 AM »

Have you come up with any ideas?
Try to write the expression for the potential of the hydrogen half-cell...
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sharonjh

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Re: EMF
« Reply #2 on: September 11, 2010, 01:56:07 AM »

The potential for H2 is 0 so does this mean the NaOH will have no affect on the EMF?
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MrTeo

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Re: EMF
« Reply #3 on: September 11, 2010, 06:44:17 AM »

The potential for H2 is 0 so does this mean the NaOH will have no affect on the EMF?

There's no point in guessing the answer...
Try to write the expression for the potential of the hydrogen half-cell.
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The way of the superior man may be compared to what takes place in traveling, when to go to a distance we must first traverse the space that is near, and in ascending a height, when we must begin from the lower ground. (Confucius)

sharonjh

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Re: EMF
« Reply #4 on: September 11, 2010, 01:51:55 PM »

The potential for H2 is 0 so does this mean the NaOH will have no affect on the EMF?

There's no point in guessing the answer...
Try to write the expression for the potential of the hydrogen half-cell.

2H+(aq) + 2e- → H2(g) v=0.00

Do I need to use the Nernst equation?
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MrTeo

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Re: EMF
« Reply #5 on: September 11, 2010, 08:19:28 PM »


2H+(aq) + 2e- → H2(g) v=0.00

Do I need to use the Nernst equation?

Yes, that's exactly what you have to use... try to find out how E changes when [H+ (to be precise you should have written H3O+) decreases (due to the NaOH added).
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The way of the superior man may be compared to what takes place in traveling, when to go to a distance we must first traverse the space that is near, and in ascending a height, when we must begin from the lower ground. (Confucius)

sharonjh

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Re: EMF
« Reply #6 on: September 12, 2010, 01:48:13 PM »


2H+(aq) + 2e- → H2(g) v=0.00

Do I need to use the Nernst equation?

Yes, that's exactly what you have to use... try to find out how E changes when [H+ (to be precise you should have written H3O+) decreases (due to the NaOH added).

Great...thank you so much for your *delete me*
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