1. A 0.4243-g sample of CaCO 3 is dissolved in 12 MHCI and the resulting solution is diluted to 250.0 mL in avolumetric flask.
a) how many moles of the CaCO 3 are used (formula mass =100.1)?
b) what is the molarity of the CA 2+ in the 250 mL ofsolution?
c) How many moles of Ca 2+ are in a 25.00 mL aliquot of solution inlb?

2. 25.00 mL aliquots of the solution from problem 1are titrate with EDTA to the Eriochrome Black T end point. A blankcontaining a small measured amount of Mg 2+ requires 3.21 mL of theEDTA to reach the end point. An aliquot to which the same amount ofthe Mg 2+ is added requires 24.95 mL of the EDTA to reach the endpoint.
a) How many milliliters of EDTA are needed to titrate the CA 2+ ionin the aliquot?
b) How many moles of the EDTA are there in the volume obtained inpart A?
c) What is the molarity of the EDTA solution?

3. A 100-mL sample of hard water is titrated with theEDTA solution in Problem 2. The same amount of Mg 2+ is added aspreviously, and the volume of EDTA required is 31.84 mL.
a) What volume of EDTA is used in titrating the Ca 2+ in the hardwater?
b) How many moles of EDTA are there in that volume?
c) How many moles of Ca 2+ are there in the 100 mL of water?
d) If the Ca 2+ comes from CaCO 3+ How many moles of CaCO 3 arethere in one liter of the water? How many grams of CaCO 3 arepresent per liter of the water?
e) If 1 ppm CaCO 3 = 1 mg per liter, what is the water hardness inppm CaCO 3?