posted by Audrey on .
Find the pH of a solution prepared by taking a 50.0 mL aliquot of a solution prepared by dissolving 12.25g of NaOH and 250.0 mL of water and diluting that aliquot to 1.00L?
12.25 g NaOH = ?? moles
moles = grams/molar mass = 12.25/40 = about 0.3 moles (you need to do it more accurately).
Place that in 250 mL and the molarity is
M = moles/L = 0.3/0.25 = about 1.2 M.
The concn of the diluted aliquot then is about 1.2 x (50/1000) = about 0.061
This is a solution of a strong base since NaOH ionizes 100%; therefore,
pOH = -log(OH^-) = -log(0.06) = about 1.2 and pH + pOH = 14. Solve for pH.