First, we need to calculate the concentration of hydroxide ions (OH-) in the solution:
Number of moles of Ca(OH)2 = 1.40 g / 74.10 g/mol = 0.0189 mol
Volume of solution = 865 mL = 0.865 L
Concentration of OH- = 2 x 0.0189 mol / 0.865 L = 0.0437 M
From this, we can calculate the pOH:
pOH = -log[OH-] = -log(0.0437) = 1.36
Using the fact that pH + pOH = 14, we can calculate the pH:
pH = 14 - pOH = 14 - 1.36 = 12.64
So, the pH of the solution is 12.64 and the pOH is 1.36.
(If this doesn’t seem right to you make sure you comment!)