Step-by-step explanation:
The acidity of a solution can be expressed as:
pH = -log₁₀[H⁺]
Similarly, the alkalinity (basicity) of a solution can be expressed as:
pOH = -log₁₀[OH⁻].
Mathematically, pH + pOH = 14. The pH scale goes from 1 to 14. When calculating pH and pOH, you can find one of the two, and subtract the result from 14 to give you the other.
As this is an acid solution, evidently, we're going to start with pH.
HCl(aq) → H⁺(aq) + Cl⁻(aq). Hydrochloric acid is a strong acid, which means it fully dissociates. Therefore, [H⁺] = [HCl].
Hence, pH = -log₁₀[H⁺] = -log₁₀[0.001] = 3.
Therefore, pOH = 14 - pH = 11