Chemical Forums
Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: xshadow on June 23, 2022, 09:02:56 AM
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Hi!!
I have a doubt about the titration curve of a redox reaction
I have as titrand a 50ml solution of Cr3+ 0.02M and as titrant a Sn2+ 0.1M solution in HCl 1M
I know that E°(Cr3+/2+)=-0.40V while E°(Sn4+/2+) = 0.14V
I've calculated the potential E gpr phi=0.001 using thos formula
Phi<1
E=E°(Cr3+/2+) +RT/nF ln( 1-phi / phi)
I get E= -0.577V for phi=0.001
But the tritatipn curves I usually see have always positive vute for "E"
Can a negative value be possibile? Can the tritation occour anyway?
Thanksss!
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In this reaction chromium get reduced and tin oxidised. The opposit is not possible.
E = Eox- E red
Use for E the Nernst equation and the concentration of both ions.
The value should be positive.
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In this reaction chromium get reduced and tin oxidised. The opposit is not possible.
E = Eox- E red
Use for E the Nernst equation and the concentration of both ions.
The value should be positive.
You mean I have to calculatw E(Cr3+/2+ us8ng the nersy equation??
And do the same thing for Tin?
Because using the standard potential I have: -0.40 + 0.14 = negqtive value
Using the nernst equation will be ok?
Thanks v)
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No it's opposit 0,14V -(-0,4V) = 0,54 V for E0 if both have same concentration.
But you have to develop E = E0 + RT/zF ln cox/cred for both elements
https://www.google.com/url?q=https://m.youtube.com/watch%3Fv%3DjousNNceCXs&sa=U&ved=2ahUKEwjHxoHy4MP4AhWASfEDHazLD-0QtwJ6BAgEEAE&usg=AOvVaw1lNWWG0OJeQ1QH3ngziGNm
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No it's opposit 0,14V -(-0,4V) = 0,54 V for E0 if both have same concentration.
But you have to develop E = E0 + RT/zF ln cox/cred for both elements
https://www.google.com/url?q=https://m.youtube.com/watch%3Fv%3DjousNNceCXs&sa=U&ved=2ahUKEwjHxoHy4MP4AhWASfEDHazLD-0QtwJ6BAgEEAE&usg=AOvVaw1lNWWG0OJeQ1QH3ngziGNm
But if Cr3+ is reduced it means it's the catodhe so the correct formula should be:
E cathode - E anode= E(Cr3+/2+) - E(Sn4+/2+)= -0.40 -(0.14)
The opposite!!... ???
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In this reaction chromium get reduced and tin oxidised. The opposit is not possible.
E = Eox- E red
Use for E the Nernst equation and the concentration of both ions.
The value should be positive.
Am I missing something? otherwise your equation should be E = E(red) - E(ox)
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You are right it is the opposit E = Ered- Eox
What means this reaction cannot take place. The opposit would be the case Chromium II will be oxidised by tin IV to chromium III and tin II.