acid-base problem

Question

A solution containing water has a .[H3O]+ = 1.57 x 10^-13

a.) What is the [OH]-

b.) Justify whether the solution is acidic, basic, or neutral.

Answer 1

For part A, you were given the concentration of the hydronium ion which can be used to find the concentration of the hydroxide ion by combining the following equations

Equation 1: pH = -log([H₃O⁺])

Equation 2: pOH = -log([OH^-])

Equation 3: pH + pOH = 14

First find pH.

using equation 1, pH = -log(1.57x10^-13) = 12.8

NOTE: The most convenient way to answer part B is to use pH. Since we solved pH to be larger than 7, the solution is basic.

Second find pOH.

rearranging equation 3 gives pOH = 14 - pH = 14 - 12.8 = 1.2

Third find [OH^-].

rearranging equation 2 gives [OH^-] = 10^(-pOH) = 10^(-1.2) = 6.3x10^-2