Question

A 1.105-g sample of an unknown monoprotic acid is dissolved in water and titrated with standardized 0.122 M NaOH solution. A volume of 22.98 mL of the NaOH solution is required to reach the endpoint. Calculate the molar mass of the unknown acid.

Answer 1

To calculate the molar mass of the unknown monoprotic acid, first determine the number of moles of NaOH used in the titration. Since the acid is monoprotic, it equals the number of moles of acid. Then divide the sample's mass by the moles of acid to obtain the molar mass.

Step-by-step explanation:

The subject of this question is Chemistry, specifically relating to a laboratory technique known as titration which is often utilized to determine the concentration of a solution or the molar mass of an unknown compound. To calculate the molar mass of the unknown acid from the titration data, several steps must be followed:

1. First, calculate the number of moles of NaOH used to titrate the unknown acid using the concentration and volume: moles of NaOH = volume in L × molarity.
2. For a monoprotic acid, which donates one proton per molecule, the number of moles of NaOH will equal the number of moles of the acid.
3. Then, use the mass of the unknown acid and the number of moles to calculate its molar mass: molar mass = mass in g / moles of acid.

Applying these steps to the provided data:

• Number of moles of NaOH = 0.02298 L × 0.122 M = 0.002804 mol NaOH
• The number of moles of the unknown acid, therefore, is also 0.002804 mol.
• The molar mass of the unknown acid = 1.105 g / 0.002804 mol = 393.73 g/mol