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Ch.16 - Acid-Base Equilibria
Brown - Chemistry: The Central Science 15th Edition
Brown15th EditionChemistry: The Central ScienceISBN: 9780137542970Not the one you use?Change textbook
All textbooksBrown 15th EditionCh.16 - Acid-Base EquilibriaProblem 50c
Chapter 16, Problem 50c

Calculate [OH-] and pH for each of the following strong base solutions: (c) 10.0 mL of 0.0105 M Ca(OH)2 diluted to 500.0 mL

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Step 1: Identify the base in the solution. In this case, the base is Ca(OH)2. It's a strong base, which means it will dissociate completely in water to form Ca2+ and 2OH- ions.
Step 2: Calculate the initial concentration of OH- ions. Since each Ca(OH)2 molecule produces 2 OH- ions, the initial concentration of OH- ions is twice the concentration of Ca(OH)2. In this case, the initial concentration of OH- ions is 2 * 0.0105 M = 0.021 M.
Step 3: Calculate the final concentration of OH- ions after dilution. The formula for dilution is M1V1 = M2V2, where M1 and V1 are the initial molarity and volume, and M2 and V2 are the final molarity and volume. In this case, M1 = 0.021 M, V1 = 10.0 mL, and V2 = 500.0 mL. Solve for M2 to find the final concentration of OH- ions.
Step 4: Calculate pOH using the formula pOH = -log[OH-]. Use the final concentration of OH- ions from step 3.
Step 5: Calculate pH using the formula pH = 14 - pOH. Use the pOH value from step 4.

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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). Understanding the dissociation of strong bases is crucial for calculating hydroxide ion concentration in solution.
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Dilution

Dilution is the process of reducing the concentration of a solute in a solution, typically by adding more solvent. The dilution equation, C1V1 = C2V2, relates the initial concentration and volume to the final concentration and volume. This concept is essential for determining the new concentration of hydroxide ions after the solution is diluted to a specific volume.
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pH and pOH Calculations

pH and pOH are measures of the acidity and basicity of a solution, respectively. The pH scale ranges from 0 to 14, with lower values indicating higher acidity and higher values indicating higher basicity. The relationship between pH and pOH is given by the equation pH + pOH = 14. For strong bases, calculating pOH from the hydroxide ion concentration allows for the determination of pH.
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