Calculate the pH of 0,3g calcium hydroxide dissolved in water to give 500ml solution.

Answer 1

mols Ca(OH)2 = grams/molar mass.
mols OH^- = 2x that
M OH^- = mols OH^-/L solution
pOH = -log(OH^-)
pH + pOH = pKw = 14.
After you have pOH you have pKw, solve for pH.