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Ch.17 - Aqueous Ionic Equilibrium
Chapter 17, Problem 7

A 15.0-mL sample of 0.100 M Ba(OH)2 is titrated with 0.125 M HCl. Calculate the pH for at least five different points throughout the titration curve and sketch the curve. Indicate the volume at the equivalence point on your graph.

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<insert step 1: Determine the initial pH of the Ba(OH)_2 solution before any HCl is added. Calculate the concentration of OH^- ions using the formula [OH^-] = 2 * [Ba(OH)_2] because each Ba(OH)_2 dissociates into two OH^- ions. Then, find the pOH and convert it to pH using pH + pOH = 14.>
<insert step 2: Calculate the pH after adding a small volume of HCl, such as 5.0 mL. Determine the moles of HCl added and the moles of OH^- initially present. Subtract the moles of HCl from the moles of OH^- to find the remaining moles of OH^-. Calculate the new concentration of OH^- and find the pH.>
<insert step 3: Determine the pH at the equivalence point. At this point, all the OH^- ions have reacted with HCl, forming water and BaCl_2. Calculate the volume of HCl needed to reach the equivalence point using the stoichiometry of the reaction. Since the solution is neutral at the equivalence point, the pH is 7.>
<insert step 4: Calculate the pH after adding a volume of HCl beyond the equivalence point, such as 20.0 mL. Determine the excess moles of HCl and calculate the concentration of H^+ ions in the solution. Use this concentration to find the pH.>
<insert step 5: Sketch the titration curve using the calculated pH values at different points. Label the initial pH, the pH at the equivalence point, and the pH after adding excess HCl. Indicate the volume of HCl at the equivalence point on the graph.>