If 80g of NaOH is added to 100mL water, what is the pH of the resulting solution?

Answer 1

moles NaOH = grams/molar mass
M NaOH = moles NaOH/L solution.
(OH^-) = (NaOH)
pOH = -log(OH^-), then convert to pH by
pH + pOH = pKw = 14'=

Technically, this is not the correct answer. Technically, the correct answer cannot be obtained UNLESS one knows the density of the solution. The reason is that the definition of M is moles/L of solution and the problem doesn't say that; i.e., it asks, "If 80 g NaOH is ADDED TO 100 mL water....." That will produce MORE than 100 mL of solution and without the density the volume of the solution is unknown. However, I think the spirit of the problem is to assume the density of the solution is 1.0 g/mL which means the solution is 100 mL.