(a) A 0.1044-g sample of an unknown monoprotic acid requires 22.10 mL of 0.0500 M NaOH to reach the end point. What is the molar mass of the unknown?

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Identify that the problem involves a titration of a monoprotic acid with NaOH, where the acid reacts with NaOH in a 1:1 molar ratio.

Calculate the moles of NaOH used in the titration using the formula: \( \text{moles of NaOH} = \text{volume (L)} \times \text{molarity (M)} \).

Since the acid is monoprotic, the moles of acid will be equal to the moles of NaOH at the endpoint.

Use the mass of the acid sample and the moles of acid to calculate the molar mass of the acid using the formula: \( \text{molar mass} = \frac{\text{mass of acid (g)}}{\text{moles of acid}} \).

Ensure all units are consistent and check calculations for accuracy.

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Key Concepts

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

Monoprotic Acid

A monoprotic acid is an acid that can donate only one proton (H⁺ ion) per molecule during a chemical reaction. This characteristic is crucial for understanding acid-base reactions, as it determines the stoichiometry of the reaction with a base, such as sodium hydroxide (NaOH). In this case, the amount of NaOH used will directly relate to the amount of the monoprotic acid present in the sample.

Molarity and Volume Relationship

Molarity (M) is a measure of concentration defined as the number of moles of solute per liter of solution. The relationship between molarity, volume, and moles is given by the equation: moles = molarity × volume. In this problem, the volume of NaOH used allows us to calculate the moles of NaOH, which equals the moles of the monoprotic acid at the equivalence point, enabling the determination of the acid's molar mass.

Molar Mass Calculation

Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). To find the molar mass of the unknown acid, we use the formula: molar mass = mass of the sample (g) / moles of the acid. By calculating the moles of the acid from the moles of NaOH used, we can determine the molar mass, which is essential for identifying the unknown acid.

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