Can the Nernst equation be expressed directly in terms of concentrations?
Yes, it can.
The Nernst equation is an expression that relates the cell potential of an electrochemical cell to the standard cell potential, temperature, and reaction quotient.
All we have to do is insert the expression for the reaction quotient.
For the cell reaction
aA + bB → cC + dD
So we can write the Nernst equation as