1. A 0.5100 g sample of CaCO3 is dissolved in 12 M HCl and the resulting solution is diluted to 250.0 mL in a volumetricflask.
a. How many moles of CaCO3 are used (M.W. = 100.1g/mol)? I got .0051 mol
b. What is the molarity of the Ca2+ in the 250 mL ofsolution? I got .020 M
c. How many moles of Ca2+ are in a 25.0 mL aliquot(small testportions) of the solution in b.? I got .0005 mol
2. 25.0 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 Mg2+ requires 2.50 mL of the EDTA to reach the end point. An aliquot to which the same amount of Mg2+ is addedrequires 28.55 mL of teh EDTA to reach the end point.
a. How many mL of the EDTA are needed to titrate the Ca2+ ion inthe aliquot? I guessed 20 mL
b. How many moles of EDTA are there in volume obtained in a.? Iguessed .0051 mol
c. What is Molarity of the EDTA solution? I put .000010 M
3. A 100 mL sample of hard water is titrated with the EDTA solutionin problem 2. The same amount of Mg2+ is added,, and the volume of EDTA required is 22.51 mL.
a. what is the volume of EDTA used in titrating the Ca2+?
b. How many moles of EDTA are there in that volume?
c. How many moels of Ca2+ are there in 100 mL of water?