Sodium hydroxide (NaOH) is a strong base, meaning it completely dissociates in water. Strong bases do not have a pKa value.

Here's why:

* pKa is defined for acids. It measures the tendency of an acid to donate a proton (H+).

* Sodium hydroxide is a base, meaning it accepts protons.

* Strong bases have a very weak conjugate acid. The conjugate acid of NaOH is water (H2O), which is a very weak acid.

Therefore, it's not meaningful to talk about the pKa of sodium hydroxide. Instead, we describe its strength as a base.