part 2 Advance Study Assignment: Determination of the Hardness of Water 1. A 0.3
ID: 1047472 • Letter: P
Question
part 2
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 How many moles of CacO, are used (formula mass 100.1)? b. What is the molarity of the Ca in the 250 ml of solution? 0.016 M How many moles of Ca+ are in a 25.00-mL aliquot of the solution in 1b? c. 2. 25.00-mL aliquots of the solution from Problem I are titrated with EDTA to the Eriochrome Black T end point. A blank containing a small measured amount of Mg+ requires 2.77 mL of the EDTA to reach the end point. An aliquot to which the same amount of Mg is added requires 39.04 mL of the EDTA to reach the end point a. How many milliliters of EDTA are needed to titrate the Ca ion in the aliquot? 31.otn-2.77mi b. How many moles of EDTA are there in the volume obtained in Part a? moles c. What is the molarity of the EDTA solution? 00327 L (continued on following page)Explanation / Answer
Ans 1 :
a) Number of moles of CaCO3 = weight / molar mass
= 0.3946 / 100.1
= 0.003942 moles
b) Molarity = number of moles of CaCO3 / volume of solution in L
= 0.003942 / 0.250
= 0.0158 M
c) Number of moles in 25 mL = 0.0158 x 0.025
= 3.94 x 10-4 moles
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