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Ch.17 - Aqueous Ionic Equilibrium
Tro - Chemistry: A Molecular Approach 4th Edition
Tro4th EditionChemistry: A Molecular ApproachISBN: 9780134112831Not the one you use?Change textbook
All textbooksTro 4th EditionCh.17 - Aqueous Ionic EquilibriumProblem 39c
Chapter 17, Problem 39c

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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Step 1: The Henderson-Hasselbalch equation is given by pH = pKa + log([A-]/[HA]). Here, [A-] is the concentration of the base (NaC2H3O2) and [HA] is the concentration of the acid (HC2H3O2).
Step 2: First, calculate the molar mass of HC2H3O2 and NaC2H3O2. Then, use these values to convert the given masses (10.0 g each) into moles.
Step 3: Next, calculate the molarities of HC2H3O2 and NaC2H3O2 by dividing the number of moles by the volume of the solution in liters (150.0 mL = 0.150 L).
Step 4: The pKa value for HC2H3O2 (acetic acid) is 4.76. Substitute the calculated molarities and the pKa value into the Henderson-Hasselbalch equation.
Step 5: Solve the equation to find the pH of the solution. Remember, the log function in the equation is base 10.

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Key Concepts

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

Henderson-Hasselbalch Equation

The Henderson-Hasselbalch equation is a mathematical formula used to calculate the pH of a buffer solution. 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 particularly useful for solutions containing a weak acid and its conjugate base.
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Buffer Solutions

Buffer solutions are mixtures that can resist changes in pH upon the addition of small amounts of acid or base. They typically consist of a weak acid and its conjugate base, which work together to neutralize added acids or bases. In the context of the question, the acetic acid (HC2H3O2) and sodium acetate (NaC2H3O2) form a buffer system that helps maintain a stable pH.
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Concentration Calculations

To apply the Henderson-Hasselbalch equation, it is essential to calculate the concentrations of the acid and its conjugate base in the solution. Concentration is defined as the amount of solute divided by the volume of solution. In this case, the masses of HC2H3O2 and NaC2H3O2 must be converted to moles using their molar masses, and then divided by the total volume of the solution (in liters) to find the necessary concentrations for the equation.
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Related Practice
Textbook Question

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

Textbook Question

Calculate the pH of the solution that results from each mixture. a. 50.0 mL of 0.15 M HCHO2 with 75.0 mL of 0.13 M NaCHO2

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Textbook Question

A buffer contains significant amounts of ammonia and ammonium chloride. Write equations showing how this buffer neutralizes added acid and added base.

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Textbook Question

Use the Henderson–Hasselbalch equation to calculate the pH of each solution in Problem 29.

Textbook Question

Calculate the pH of the solution that results from each mixture. b. 125.0 mL of 0.10 M NH3 with 250.0 mL of 0.10 M NH4Cl