I have no idea how to start this one
Given a measured cell potential, Ecell = -0.3559V at 25oC, calculate the H+ concentration (M) if a reaction involves 0.813 atm H2 gas with a platinum electrode and 1.00 M Cd2+ in contact with Cd(s).
What Eo values are you using for Cd and H.
To solve this problem, you can use the Nernst equation, which relates the measured cell potential (Ecell) to the concentrations of the reactants and products in a redox reaction. The Nernst equation is given by:
Ecell = E°cell - (0.0592/n) * log(Q)
Where E°cell is the standard cell potential, n is the number of moles of electrons transferred in the balanced redox reaction, and Q is the reaction quotient.
In this case, we are given the measured cell potential (Ecell) at 25oC. We need to find the H+ concentration (M). To do this, we'll follow these steps:
Step 1: Determine the balanced equation for the redox reaction.
We know that H2 gas is involved with a platinum electrode and Cd2+ in contact with Cd(s). Let's write the balanced equation:
H2(g) + Cd2+(aq) → 2H+(aq) + Cd(s)
Step 2: Find the standard cell potential, E°cell.
We can use the standard reduction potentials (E°red) to calculate E°cell. We need to look up the reduction potentials for the half-reactions involved. Given that hydrogen gas is involved, we use the reduction potential for the hydrogen half-reaction:
H2(g) → 2H+(aq) + 2e-
The reduction potential for this half-reaction at standard conditions can be found in a table of reduction potentials. Let's say the reduction potential for the hydrogen half-reaction is E°red(H2). Then, the standard cell potential is given by:
E°cell = E°red(H2) + E°red(Cd2+)
Step 3: Calculate Q, the reaction quotient.
Based on the balanced equation, we can write the reaction quotient as follows:
Q = [H+]^2 / [Cd2+]
Step 4: Substitute the known values into the Nernst equation.
Plug in the values you know into the Nernst equation:
Ecell = E°cell - (0.0592/n) * log(Q)
In this case, n = 2, as two electrons are transferred in the balanced redox reaction (H2(g) → 2H+(aq)). The temperature is given as 25oC, but we need to convert it to Kelvin by adding 273 to get 298 K.
Step 5: Solve for [H+].
Rearrange the Nernst equation to solve for [H+].
[H+] = 10^((E°cell - Ecell) / (0.0592/n))
Finally, substitute the known values into the equation and evaluate to find the H+ concentration.