. Calculate the pH and pOH for each of the following solutions:

Question

1.8 * 10-4 M NaOH

Answer 1

Sodium hydroxide, NaOH, is a strong base meaning it completely dissociates:

NaOH ---> Na⁺ + OH^- (stoichiometry of the balanced equation is 1 NaOH : 1 Na+ : 1 OH-).

So 1.80 x 10^-4 M NaOH produces 1.80x10^-4 M Na+ ions and 1.80x10^-4 M OH- ions so we can use this concentration of OH- directly to find the pOH

pOH = -log[OH-] = -log(1.80 x 10^-4) = 3.745

Knowing that pH + pOH = 14 then pH = 14 - pOH

pH = 14 - 3.745 = 10.255 (The pH > 7 which is what we expect for a basic solution so our answer makes sense.)

Hope this helps!