Step 1:

The equilibrium constant K is 1.8 * 10^-7

Concentration of $\"\"$ .

The chemical reaction is $\"\"$ .

Definition of equilibrium constant:

Equilibrium constant $\"\"$ .

Substitute K is 1.8 * 10-7 and $\"\"$ in the above formula.

$\"\"$

Concentration of $\"\"$ is $\"\"$ .

Solution:

Concentration of $\"\"$ is $\"\"$ .