Question

Pt(s) | H2(g, 2.0 bar) | H+ (pH = 3.0) || Cl -(aq, 0.85 mol·L-1)) | Hg2Cl2(s) | Hg(l)

I need to calculate the voltage for the cell.

I have used 1E-3 M for my concentration of H+ given the pH=3 . I don't know how to incorporate the 2.0 bar into the nernst equation. I keep coming up with -.1833 V but that is incorrect.

Answer 1

The bar goes in for partial pressure of H2 gas so if we have
H2 ==> 2H^+ + 2e then

E = Eo - (0.059/2)*log [(H^+)^2/pH2]
I'm unclear if the bar has become the standard of if your prof is using 1 atm for the standard. The difference
a. if bar is standard, you simply substitute 2 for partial pressur.
b. if atm is standard, you convert 2 bar to atm.
c. In any even, the difference between bar and atm is small. 1 bar = 0.9869 atm.