Two 25.0-mL samples, one 0.100 M HCl and the other 0.100 M HF, are titrated with 0.200 M KOH. a. What is the volume of added base at the equivalence point for each titration?

Name: Chemistry: A Molecular Approach
Author: Tro
ISBN: 9780134874371

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Step 1: Identify the reaction for each titration. For HCl, the reaction is HCl + KOH -> KCl + H2O. For HF, the reaction is HF + KOH -> KF + H2O.

Step 2: Calculate the moles of acid in each sample. Use the formula: moles = concentration (M) * volume (L). For both HCl and HF, moles = 0.100 M * 0.025 L.

Step 3: Determine the moles of KOH needed to reach the equivalence point. At the equivalence point, moles of KOH = moles of acid, since the reaction is a 1:1 stoichiometry.

Step 4: Calculate the volume of KOH solution required to provide the necessary moles of KOH. Use the formula: volume (L) = moles of KOH / concentration of KOH (M).

Step 5: Convert the volume of KOH from liters to milliliters by multiplying by 1000, as the final answer should be in mL.

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Titration and Equivalence Point

Titration is a quantitative analytical method used to determine the concentration of a solution by reacting it with a standard solution. The equivalence point is reached when the amount of titrant added is stoichiometrically equivalent to the amount of substance in the sample. This point is crucial for calculating the volume of titrant needed, as it indicates complete neutralization of the acid by the base.

Molarity and Volume Relationships

Molarity (M) is defined as the number of moles of solute per liter of solution. In titration calculations, the relationship between the molarity of the acid and the base, along with their respective volumes, is used to determine the volume of titrant required at the equivalence point. The formula M1V1 = M2V2 helps in calculating the volumes needed for neutralization, where M1 and V1 are the molarity and volume of the acid, and M2 and V2 are those of the base.

Strong vs. Weak Acids

Strong acids, like HCl, completely dissociate in solution, while weak acids, like HF, only partially dissociate. This difference affects the pH at the equivalence point and the stoichiometry of the titration. Understanding the nature of the acids involved is essential for accurately determining the volume of base needed, as it influences the calculation of the equivalence point and the resulting pH of the solution.