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Ch.17 - Additional Aspects of Aqueous Equilibria
Brown - Chemistry: The Central Science 14th Edition
Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232Not the one you use?Change textbook
All textbooksBrown 14th EditionCh.17 - Additional Aspects of Aqueous EquilibriaProblem 48b
Chapter 17, Problem 48b

Calculate the pH at the equivalence point in titrating 0.100 M solutions of each of the following with 0.080 M NaOH: (b) chlorous acid (HClO2).

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Identify the type of titration: This is a weak acid (HClO_2) being titrated with a strong base (NaOH).
At the equivalence point, all the weak acid (HClO_2) has been converted to its conjugate base (ClO_2^-).
Calculate the concentration of the conjugate base (ClO_2^-) at the equivalence point using the initial concentrations and volumes of the acid and base.
Use the hydrolysis of the conjugate base (ClO_2^-) to find the concentration of OH^- ions: ClO_2^- + H_2O \(\rightleftharpoons\) HClO_2 + OH^-.
Calculate the pOH from the concentration of OH^- ions, and then find the pH using the relation pH + pOH = 14.

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Key Concepts

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

Titration and Equivalence Point

Titration is a quantitative analytical method used to determine the concentration of a solute in a solution. The equivalence point occurs when the amount of titrant added is stoichiometrically equivalent to the amount of analyte in the solution, resulting in complete neutralization. At this point, the pH of the solution is determined by the properties of the resulting products, rather than the original acid or base.
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Equivalence Point in Titration

Weak Acid and Its Conjugate Base

Chlorous acid (HClO2) is a weak acid that partially dissociates in solution. At the equivalence point of its titration with a strong base like NaOH, the resulting solution contains the conjugate base (ClO2-) of the weak acid. The pH at this point is influenced by the hydrolysis of the conjugate base, which can affect the concentration of hydroxide ions in the solution, thus impacting the overall pH.

pH Calculation from Hydrolysis

To calculate the pH at the equivalence point, one must consider the hydrolysis of the conjugate base formed during the titration. The equilibrium established by the hydrolysis reaction can be described by the Kb expression, which relates the concentrations of the products and reactants. By determining the concentration of hydroxide ions produced and converting this to pH, one can accurately find the pH of the solution at the equivalence point.
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pH Calculation Example
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Textbook Question

Calculate the pH at the equivalence point in titrating 0.100 M solutions of each of the following with 0.080 M NaOH: (c) benzoic acid (C6H5COOH).

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Textbook Question

(a) True or false: 'solubility' and 'solubility-product constant' are the same number for a given compound.

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The solubility of two slightly soluble salts of M2 + , MA and MZ2, is the same, 4 * 10-4 mol/L. (c) If you added an equal volume of a solution saturated in MA to one saturated in MZ2, what would be the equilibrium concentration of the cation, M2+?

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Textbook Question

Consider the titration of 30.0 mL of 0.050 M NH3 with 0.025 M HCl. Calculate the pH after the following volumes of titrant have been added: (b) 20.0 mL (c) 59.0 mL.

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Textbook Question

Calculate the pH at the equivalence point for titrating 0.200 M solutions of each of the following bases with 0.200 M HBr: (b) hydroxylamine 1NH2OH2.

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Consider the titration of 30.0 mL of 0.050 M NH3 with 0.025 M HCl. Calculate the pH after the following volumes of titrant have been added: (e) 61.0 mL (f) 65.0 mL.

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