The following voltaic cell registers an E cell = 0.100V.
Pt|H2(g 1 atm)|H^+(x M)||H^+(1.0 M)|H2(g 1 atm)
What is the pH of the unknown solution?
I am completely baffled as I was not aware until I read this question that pH could be found from voltaic cells. Any help would be greatly appreciated.
The anode is H2 ==> 2H^+ + 2e
The cathode is 2H^+ + 2e ==> H2
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The cell is H2+2H^+==>2H^+ + H2
Ecell = Eocell -(0.0592/2)logQ
log Q = (H^+)^2*pH2/(H^+)^2*pH2
H^+ in numerator is the unknown; H^+ in denominator is 1M. pH2 is 1atm in both cases. Solve for (H^+) and convert to pH. Ecell is 0.1.
How am I able to solve for [H^+] when I don't have Q and can't rearrange?
Ecell=E*cell-0.0592/2*log[xM]/[1.0]
-3.378 = log[xM]/[1.0M]
x=0.0000410 M
pH=3.38
What did I do wrong because this is not the right answer
-3.378 is right but x is not.
First, -3.378 = log X^2
4.19E-4 = x^2 and not E-5 as you have.
Second, you didn't take the square root.
Third, if 4.10E-5 were the right answer, -log of that for pH is not right.
So -3.378 = log x^2 and solve for x, then convert to pH.
To determine the pH of the unknown solution in this voltaic cell setup, you can use the Nernst equation. The Nernst equation is given by:
Ecell = E°cell - (0.0592/n) * log(Q)
Where:
- Ecell is the cell potential
- E°cell is the standard cell potential
- n is the number of electrons transferred in the balanced equation
- Q is the reaction quotient, which can be calculated by dividing the concentrations of the products by the concentrations of the reactants, with each concentration raised to the power of its stoichiometric coefficient.
In this case, the half-reactions occurring in the cell are:
Anode: H2(g) → 2H+(aq) + 2e-
Cathode: 2H+(aq) + 2e- → H2(g)
Since the cell voltage is given as 0.100V, this means that Ecell = 0.100V.
To use the Nernst equation, you need to know the standard cell potential (E°cell) of the reaction. However, the standard cell potential is not provided in the question. Therefore, we cannot calculate the pH of the unknown solution using the information provided.
pH is typically determined using a pH meter or indicators, rather than relying on voltaic cells. If you have access to the standard reduction potential of the half-reaction for the system, you can calculate the pH using the Nernst equation. Otherwise, more information or a different approach would be required to find the pH of the unknown solution in this scenario.