Textbook Question
Use the Henderson–Hasselbalch equation to calculate the pH of each solution. c. a solution that contains 10.0 g of HC2H3O2 and 10.0 g of NaC2H3O2 in 150.0 mL of solution
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Ch.17 - Aqueous Ionic Equilibrium
Chapter 17, Problem 42
Calculate the pH of the solution that results from each mixture. a. 150.0 mL of 0.25 M HF with 225.0 mL of 0.30 M NaF b. 175.0 mL of 0.10 M C2H5NH2 with 275.0 mL of 0.20 M C2H5NH3Cl
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Identify the type of solution formed in each case. For part (a), mixing HF and NaF forms a buffer solution of a weak acid (HF) and its conjugate base (F⁻). For part (b), mixing C₂H₅NH₂ and C₂H₅NH₃Cl forms a buffer solution of a weak base (C₂H₅NH₂) and its conjugate acid (C₂H₅NH₃⁺).
Use the Henderson-Hasselbalch equation to calculate the pH of the buffer solutions. For part (a), use the equation: pH = pKa + log([A⁻]/[HA]), where [A⁻] is the concentration of F⁻ and [HA] is the concentration of HF. For part (b), use the equation: pH = pKa + log([B]/[BH⁺]), where [B] is the concentration of C₂H₅NH₂ and [BH⁺] is the concentration of C₂H₅NH₃⁺.
Calculate the moles of each component in the mixtures. For part (a), moles of HF = 0.25 M * 0.150 L and moles of NaF = 0.30 M * 0.225 L. For part (b), moles of C₂H₅NH₂ = 0.10 M * 0.175 L and moles of C₂H₅NH₃Cl = 0.20 M * 0.275 L.
Determine the concentrations of each component in the final solution by dividing the moles by the total volume of the mixture. For part (a), total volume = 150.0 mL + 225.0 mL. For part (b), total volume = 175.0 mL + 275.0 mL.
Substitute the concentrations into the Henderson-Hasselbalch equation to find the pH of each buffer solution.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Buffer Solutions
Buffer solutions are mixtures of a weak acid and its conjugate base or a weak base and its conjugate acid. They resist changes in pH when small amounts of acid or base are added. In the given question, the mixtures of HF and NaF, as well as C2H5NH2 and C2H5NH3Cl, form buffer systems that can be analyzed using the Henderson-Hasselbalch equation.
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Buffer Solutions
Henderson-Hasselbalch Equation
The Henderson-Hasselbalch equation is a mathematical formula used to calculate the pH of buffer solutions. It is expressed as pH = pKa + log([A-]/[HA]), where pKa is the negative logarithm of the acid dissociation constant, [A-] is the concentration of the conjugate base, and [HA] is the concentration of the weak acid. This equation is essential for determining the pH of the mixtures in the question.
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Dilution and Concentration Calculations
Dilution involves reducing the concentration of a solute in a solution, typically by adding more solvent. The total volume and concentrations of the components in the mixtures must be calculated to determine the final concentrations of the acid and base in the buffer solutions. Understanding dilution principles is crucial for accurately calculating the pH of the resulting solutions.
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Related Practice
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