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Ch.17 - Acids and Bases
Chapter 17, Problem 82d

For each strong base solution, determine [OH], [H3O+], pH, and pOH. d. 5.0×10–4 M Ca(OH)2

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Identify that calcium hydroxide, Ca(OH)_2, is a strong base and dissociates completely in water.
Write the dissociation equation: Ca(OH)_2 \rightarrow Ca^{2+} + 2OH^{-}.
Calculate the concentration of OH^{-} ions. Since each formula unit of Ca(OH)_2 produces two OH^{-} ions, multiply the concentration of Ca(OH)_2 by 2.
Use the concentration of OH^{-} to find pOH using the formula: \text{pOH} = -\log[OH^{-}].
Calculate the pH using the relationship: \text{pH} + \text{pOH} = 14.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Strong Bases

Strong bases are substances that completely dissociate in water to produce hydroxide ions (OH-). Common examples include alkali metal hydroxides and alkaline earth metal hydroxides, such as calcium hydroxide (Ca(OH)2). The concentration of the base directly affects the concentration of OH- ions in solution.
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pH and pOH Calculations

pH and pOH are measures of the acidity and basicity of a solution, respectively. pH is calculated as the negative logarithm of the hydronium ion concentration ([H3O+]), while pOH is the negative logarithm of the hydroxide ion concentration ([OH-]). The relationship between pH and pOH is given by the equation pH + pOH = 14 at 25°C.
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Ion Product of Water

The ion product of water (Kw) is the equilibrium constant for the self-ionization of water, defined as Kw = [H3O+][OH-] = 1.0 x 10^-14 at 25°C. This relationship allows for the calculation of [H3O+] from [OH-] and vice versa, which is essential for determining the pH and pOH of a solution when the concentration of a strong base is known.
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