If the concentration of the solutions are doubled then the cell EMF is also doubled.
According to the Nernst equation, the concentration of the species determines the cell EMF as we can see form the formula;
Ecell = E°cell - 0.0592/nlogQ.
Hence, if the concentration of the solutions are doubled then the cell EMF is also doubled.
Learn more about Nernst equation:https://brainly.com/question/13043546