if i am not mistake u can use -log[concentration of oh-] to find it ie -log[6.4*10^-10]=9.19

Answer: Yes. The pH = 7.6 . ___________________________________________________ Explanation: ____________________________________________________ pH = - log [H⁺] ; in which, by convention, we assume that there is an implied "base 10" if there is no number listed as a "base" under the "log" sign; i.e. , " pH = - log [H⁺]⁺ = - log₍₁₀₎ [H⁺] ; ________________________________________________ in which, the: " [H⁺] " refers to the concentration of hydrogen ions, or " H⁺ " ; in "Molarity" ; that is: "moles of solutes per Liters of solution", or "mol / L", or "M" . ________________________________________________ Likewise, "pOH = - log [OH⁻] = - log₍₁₀₎ [OH⁻] " . ________________________________________________ Note: pH + pOH = 14 . ________________________________________________ So, given: "A solution with 6.4 * 10⁻¹⁰ M OH (in our problem), find the "pH". _________________________________________________ The pOH of the solution is 6.4 . _________________________________________________ Since pH + pOH = 14 ; we can substitute "6.4" for "pOH" ; and solve for "pH": _________________________________________________ pH + 6.4 = 14 ; Subtract "6.4" from each side of the equation; to isolate "pH" on one side of the equation; and to solve for the "pH" ; _________________________________________________ pH + 6.4 − 6.4 = 14 − 6.4 ; _________________________________________________ pH = 7.6 . _________________________________________________