Question

A 25 mL sample of hard water is titrated with a 0.001 M solution of EDTA, and the end point of the titration is reached at 50 mL of EDTA added. What is the concentration of Ca$^{2+}$ and Mg$^{2+}$ ions in solution?

• A. 0.0005 M
• B. 0.001 M
• C. 0.002 M
• D. 0.006 M

Hint:

When titrating water samples, the concentration of metal ions is related to the volume of EDTA used, based on the stoichiometry of the reaction.

Answer 1

The Correct Option is A

Using the volume of EDTA required to reach the end point and the molarity of EDTA, the concentration of Ca$^{2+}$ and Mg$^{2+}$ ions in the sample is calculated to be 0.0005 M.