A saturated aqueous solution of calcium hydroxide is approximately 0.13% calcium hydroxide,by mass,and has a density of 1.02 g ml^-1.What is the pH of such a solution? A)11.95 B)12.25 C)12.55 D)12.75 E)13.00

Question

Quizplus · Accepted Answer

First, we need to write the equation for the dissociation of calcium hydroxide:
Ca(OH)2 → Ca2+ + 2OH-
The concentration of Ca2+ ions in a saturated solution is negligible, so we can assume that the concentration of OH- ions is equal to the concentration of Ca(OH)2 in the solution.
Since the solution is approximately 0.13% Ca(OH)2 by mass, this means that there is 0.13 g of Ca(OH)2 per 100 g of solution.
Using the density of the solution, we can calculate the volume of 100 g of solution:
100 g / 1.02 g/ml = 98.03 ml
This means that there is 0.13 g of Ca(OH)2 in 98.03 ml of solution.
We can convert grams to moles of Ca(OH)2:
0.13 g / (74.1 g/mol) = 0.00175 mol
Finally, we can calculate the concentration of OH- ions in the solution:
2 x 0.00175 mol / 0.09803 L = 0.0357 M
Taking the negative logarithm to find the pH:
pH = -log(0.0357) = 1.45
However, this value is the pOH of the solution. To find the pH, we need to subtract the pOH from 14:
pH = 14 - 1.45 = 12.55
Therefore, the answer is C, 12.55.

A Saturated Aqueous Solution of Calcium Hydroxide Is Approximately 0