Question

A solution formed by dissolving an antacid tablet has a PH of 9.18 at 25 c. Calculate [H],[OH] and pOH.

Answer 1

NOPE.
pH = -log (H^+)
9.18 = -log(H^+) or (H^+) = 10^-9.18. OK here.
pOH + pH = 14 so pOH = 14 - pH = 14 - 9.18 = 4.82 is correct answer.
Then pOH = -log(OH^-) or (OH^-) = 10^-4.82 is correct answer.

Answer 2

[H] = 1.0 x 10^-9.18
[OH] = 1.0 x 10^-0.82
pOH = 0.82