Chapter 28, Problem 2ASA

Experiment 28 Advance Study Assignment: Determination of the Hardness of Water 1. A 0.3946 g sample of CaCO, is dissolved in 12 M HCI and the resulting solution is diluted to 250.0 mL in a volumetric flask. a. How many moles of CACO, are used (formula mass = 100.1)? moles b. What is the molarity of the Ca²* in the 250 mL of solution? M c. How many moles of Ca" are in a 25.00-mL aliquot of the solution in Ib? moles .. moles 아 Cacos 드 Weight in gram formula mass 0-3946 1001 E3.942 x 10-3 mol moles of solute Molanity Volume of solution (L) 3.942 x 1o-3 x 1000 250 0.0158 M Imol Caco, produce I mol Cast ion 0.0158 M Moles off Ca²+ = Molarity x 0.0158 Vo lume lin L) 25 1000 3.94 X10-4mol.

A 25.00 mL unknown water sample is titrated with a standardized 0.0140 M EDTA solution.  It is determined that 8.54 mL of EDTA is required to reach the end point.  The blank titre was determined to be 1.50 mL.  Determine the concentration of Calcium in the water sample in ppm.  (mwt. of CaCO3 = 100.0892 g/mol).

25.00 mL aliquots of the solution in problem 1 are titrated with EDTA to the calmagite end point. A blank containing a small measured amount of Mg^2+ requires 2.12 mL of the EDTA to reach the end point. An aliquot to which the same amount of Mg^2+ is added requires 25.88 mL of the EDTA to reach the end point.