(very) nonstandard reduction potential

In summary, the conversation discusses a question about the reduction potential required for reducing the {VO}^{2+} concentrations to {10}^{-6} M at pH = 2 at room temperature in the presence of {10}^{-4} M {V}^{3+}. The relevant equations and attempted solution are provided, with a typo in the concentration of {VO}^{2+} noted. There is also a discussion about the correct half reaction and the involvement of only one electron.
  • #1
kankerfist
35
0
I have a question that I am familiar with, but there is no answer provided and about 1000 ways to make small mistakes. I was hoping someone could take a glance and see if any mistakes jump out. Any tips would really be appreciated.
Question
What is the reduction potential required for reducing the [tex]{VO}^{2+}[/tex] concentrations to [tex]{10}^{-6}[/tex] M at pH = 2 at room temperature in the presence of [tex]{10}^{-4}[/tex] M [tex]{V}^{3+}[/tex] ?

[tex]{VO}^{2+}+2{H}^{+}+{e}^{-}[/tex] -> [tex]{V}^3{+} + {H}_{2}O[/tex]

[tex]{E}^{o}=0.34V[/tex]

Relevant Equations

[tex]
E={E}^{o}-\frac{RT}{nF}*\ln [\frac{{Products}^{sc}}{{Reactants}^{sc}}]
[/tex]
R=8.314 VC
F=96,500 C
T = 298 K
n= electrons transferred

Attempted Solution

[tex]
E={0.34}-\frac{(8.314)(298)}{(1)(96500)}*\ln [\frac{{10}^{-4}}{({10}^{-5}){(.01)}^{2}}]
[/tex]

Which is a result of pH = 2 meaning that the H+ concentration is 0.01. I left out units because LaTex got too confusing with units involved. My answer from the above attempted solution is a reduction potential of -0.0147 V.

The question then asks what would happen to the above if NaOH was added to solution. I took this to mean that NaOH fully dissolved into Na+ and OH-, increasing pH. But the question asks if the reduction would be made easier or harder... I know that lower H+ concentrations mean a more negative reduction potential, but I'm not sure how that correlates to the easiness or difficulty of reduction.
 
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  • #2
I am not familiar with using natural log (ln), so I usually change it to log
alnb = aln10logb

I wonder why in the natural log expression, the value for concentration of VO2+ is 10E-05 instead of 10E-06?

I think you wrote the wrong reaction:
First, in VO2+ V is +6, in V3+, V is +3
So you write VO2+ + 3e --> V3+
Left reaction has O, while right does not, then you add H2O to the right.
VO2+ + 3e ---> V3+ + H2O
Then balance the O
VO2+ + 3e ---> V3+ 2H2O
Then add H+ to the right
VO2+ 4H+ + 3e --> V3+ + 2H2O

Hope that will help you.
 
  • #3
It is 10^-6! That little typo caused me all kinds of headache. Also, your balanced half reaction is exactly how I would have done it too, but the one above was provided by my professor and is a valid half cell reaction. I'm not exactly sure why it is that way, but I double checked on ChemOffice and found the above reaction and also verified its standard energy of -0.337 V. I'll ask my professor why only 1 e- is involved when V is reduced by 3 and let you know what he says. Thanks for pointing out that typo, I probably would have never noticed it
 

1. What is (very) nonstandard reduction potential?

(Very) nonstandard reduction potential refers to the potential of a chemical reaction to undergo reduction under conditions that are significantly different from standard conditions. This could include extreme temperatures, pressures, or concentrations.

2. How is (very) nonstandard reduction potential measured?

(Very) nonstandard reduction potential is measured using a specialized instrument called a potentiometer. This instrument measures the voltage produced by a chemical reaction under nonstandard conditions.

3. What is the significance of (very) nonstandard reduction potential in chemistry?

(Very) nonstandard reduction potential is important because it allows scientists to understand how a chemical reaction will behave under a variety of different conditions, which is vital for applications in industries such as pharmaceuticals, agriculture, and energy production.

4. How does (very) nonstandard reduction potential differ from standard reduction potential?

Standard reduction potential refers to the potential of a reaction under specific conditions - 298K, 1 atm pressure, and 1 M concentration. (Very) nonstandard reduction potential, on the other hand, refers to the potential of a reaction under conditions that deviate significantly from these standard conditions.

5. Can (very) nonstandard reduction potential be predicted?

Yes, (very) nonstandard reduction potential can be predicted using mathematical equations and models based on the standard reduction potential and the conditions of the nonstandard reaction. However, experimental measurements are still necessary to accurately determine the (very) nonstandard reduction potential of a reaction.

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