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Ch.17 - Additional Aspects of Aqueous Equilibria
Brown - Chemistry: The Central Science 14th Edition
Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232Non è quello che usi tu?Cambia libro di testo
Tutti i libri di testoBrown 14th EditionCh.17 - Additional Aspects of Aqueous EquilibriaProblema 85
Capitolo 17, Problema 85

Furoic acid (HC5H3O3) has a Ka value of 6.76 × 10^-4 at 25 _x001F_C. Calculate the pH at 25 _x001F_C of (a) a solution formed by adding 25.0 g of furoic acid and 30.0 g of sodium furoate (NaC5H3O3) to enough water to form 0.250 L of solution; (b) a solution formed by mixing 30.0 mL of 0.250 M HC5H3O3 and 20.0 mL of 0.22 M NaC5H3O3 and diluting the total volume to 125 mL; (c) a solution prepared by adding 50.0 mL of 1.65 M NaOH solution to 0.500 L of 0.0850 M HC5H3O3.

Guida verificata passo dopo passo
1
Step 1: For part (a), calculate the molarity of furoic acid (HC5H3O3) and sodium furoate (NaC5H3O3) in the solution. Use the formula: Molarity = (mass of solute / molar mass of solute) / volume of solution in liters.
Step 2: Recognize that the solution in part (a) is a buffer solution. Use the Henderson-Hasselbalch equation: pH = pKa + log([A-]/[HA]), where [A-] is the concentration of the conjugate base (sodium furoate) and [HA] is the concentration of the acid (furoic acid).
Step 3: For part (b), calculate the initial moles of HC5H3O3 and NaC5H3O3 using their given concentrations and volumes. Then, find their concentrations in the final 125 mL solution.
Step 4: Again, use the Henderson-Hasselbalch equation for part (b) to find the pH, using the concentrations calculated in Step 3.
Step 5: For part (c), calculate the moles of NaOH added and determine the moles of HC5H3O3 remaining after the reaction with NaOH. Use the stoichiometry of the reaction to find the concentrations of the remaining acid and its conjugate base, then apply the Henderson-Hasselbalch equation to find the pH.

Concetti chiave

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Acid-Base Equilibrium

Acid-base equilibrium refers to the balance between the concentrations of acids and their conjugate bases in a solution. The dissociation constant (Ka) quantifies the strength of an acid, indicating how well it donates protons (H+) in solution. Understanding this concept is crucial for calculating pH, as it helps determine the extent of dissociation of the acid and the resulting concentrations of H+ ions.
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Triprotic Acid Equilibrium

Henderson-Hasselbalch Equation

The Henderson-Hasselbalch equation is a mathematical formula used to calculate the pH of a buffer solution. It relates the pH to the pKa of the acid and the ratio of the concentrations of the conjugate base to the acid. This equation is particularly useful in scenarios involving weak acids and their salts, such as furoic acid and sodium furoate, allowing for straightforward pH calculations in buffered solutions.
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Henderson-Hasselbalch Equation

Stoichiometry in Acid-Base Reactions

Stoichiometry involves the calculation of reactants and products in chemical reactions. In acid-base reactions, it is essential to understand the molar relationships between acids, bases, and their conjugate pairs. This concept is vital for determining the concentrations of species in solution after mixing, which directly impacts the pH calculations in the scenarios presented in the question.
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