# What are concentration cells?

May 23, 2018

A type of galvanic cell where the two half-cells are identical except for in concentration.

#### Explanation:

This is a concentration cell:

As we can see, the two half-cells are completely identical—the two electrodes are both made of solid $C u$, and the solutions both contain $C u S {O}_{4}$.

The only thing that's different in these half-cells is concentration of the $C u S {O}_{4}$—in one half cell, its concentration is $0.01 M$, and in the other, its concentration is $1 M$.

This will cause electrons to migrate in the direction that results in the increase in concentration of the $0.01 M$ $C u S {O}_{4}$ cell and the decrease in concentration of the $1 M$ cell.

So, in our case, electrons will flow from left to right.
In the left half-cell, this causes $C u \left(s\right)$ to become $C {u}^{2 +}$, increasing its concentration.
In the right half-cell, $C {u}^{2 +}$ ions reduce to become $C u \left(s\right)$, decreasing its concentration.