Given pH = 8.55 Find: [H3O+] and [OH-] Is this acidic, basic or neutral?

The given pH = 8.55

Unknown:

[H₃O⁺] = ?

[OH⁻] = ?

In order to find these unknowns we must first establish some relationship.

pH = - log[H₃O⁺]

8.55 = - log[H₃O⁺]

[H₃O⁺] = inverse log₁₀ (-8.55) = 2.82 x 10⁻⁹moldm⁻³

To find the [OH⁻],

pH + pOH = 14

pOH = 14 - pH = 14 - 8.55

pOH = 5.45

pOH = - log[OH⁻]

[OH⁻] = inverse log₁₀ (-5.45) = 3.55 x 10⁻⁶moldm⁻³

The solution is basic because it has more concentration of OH⁻ ions compared to H⁺ ions.