College

What is the pH of a 0.014 M Ca(OH)[tex]\(_2\)[/tex] solution?

A. 1.85
B. 15.85
C. 12.45
D. 12.15
E. 1.55

Answer :

To find the pH of a 0.014 M solution of Ca(OH)2, let's go through the steps:

1. Understand the Dissociation:
Calcium hydroxide, Ca(OH)2, dissociates completely in water to form calcium ions (Ca²⁺) and hydroxide ions (OH⁻). The dissociation reaction is:
[tex]\[ \text{Ca(OH)}_2 \rightarrow \text{Ca}^{2+} + 2\text{OH}⁻ \][/tex]

2. Calculate Hydroxide Ion Concentration:
Since each formula unit of Ca(OH)2 produces two hydroxide ions, the concentration of hydroxide ions (OH⁻) will be twice the concentration of the Ca(OH)2 solution.
Given: The concentration of Ca(OH)2 is 0.014 M.
Therefore, [tex]\[\text{OH}^- \text{ concentration} = 2 \times 0.014 \, \text{M} = 0.028 \, \text{M}.\][/tex]

3. Calculate pOH:
The pOH is calculated using the formula:
[tex]\[ \text{pOH} = -\log_{10}[\text{OH}^-] \][/tex]
Substituting the OH⁻ concentration, we get:
[tex]\[ \text{pOH} = -\log_{10}(0.028) \approx 1.55. \][/tex]

4. Calculate pH:
The relationship between pH and pOH is:
[tex]\[ \text{pH} + \text{pOH} = 14 \][/tex]
Given that the pOH is approximately 1.55, we can find the pH by rearranging the formula:
[tex]\[ \text{pH} = 14 - \text{pOH} = 14 - 1.55 \approx 12.45. \][/tex]

Therefore, the pH of the 0.014 M Ca(OH)2 solution is approximately 12.45.