At $298 \mathrm{~K}$, the standard reduction potential for $\mathrm{Cu}^{2+} / \mathrm{Cu}$ electrode is $0.34 \mathrm{~V}$.

Given : $\mathrm{K}_{\mathrm{sp}} \mathrm{Cu}(\mathrm{OH})_{2}=1 \times 10^{-20}$

Take $\frac{2.303 \mathrm{RT}}{\mathrm{F}}=0.059 \mathrm{~V}$

The reduction potential at $\mathrm{pH}=14$ for the above couple is $(-) x \times 10^{-2} \mathrm{~V}$. The value of $x$ is ___________