Question

A student weighed 5.616 g of ferric chloride into a beaker and added small volumes of water to dissolve it. The student then transferred the solution of ferric chloride into a 100-mL volumetric flask and filled it up to the mark. Using a pipette, 25 mL of this solution was transferred to an Erlenmeyer flask. The pH was adjusted to 7 (ferric hydroxide precipitates at high pH) and titrated with 0.150 M EDTA. The volume of EDTA required to reach the endpoint was 60.22 mL. Determine the empirical formula of ferric chloride.

Answer 1

The empirical formula of ferric chloride is FeCl3.

Step-by-step explanation:

The empirical formula of a compound gives the simplest whole-number ratio of atoms in that compound. To determine the empirical formula of ferric chloride, we first need to determine the moles of chloride and iron in the solution.

From the given information, the volume of EDTA required to reach the endpoint is 60.22 mL. Since the molar concentration of EDTA is 0.150 M, we can calculate the moles of EDTA used in the titration by multiplying the volume and molarity: 60.22 mL * 0.150 mol/L = 9.033 moles of EDTA.

According to the balanced chemical equation for the reaction between EDTA and ferric chloride, the stoichiometric ratio between them is 1:1. Therefore, the number of moles of ferric chloride in the 25 mL sample is also 9.033 moles.

To find the empirical formula of ferric chloride, we need the molar mass of ferric chloride, which is calculated as follows:

(5.616 g / 9.033 moles) = 0.621 g/mol.

This means that the empirical formula of ferric chloride is FeCl3, since the molar mass of ferric chloride (110.62 g/mol) is approximately equal to 0.621 g/mol.