Name Section Date QUESTIONS: EXPERIMENT 17 1. In a hardness of water determinati
ID: 547965 • Letter: N
Question
Name Section Date QUESTIONS: EXPERIMENT 17 1. In a hardness of water determination like the one performed in this experiment, it was found that a 25.00-mL sample of water required 12.25 mL of 0.0128 M EDTA solution for complete titration. What is the concentration (molarity) of Ca ions in the water sample? What is the concentration of CaCO, (in mg/L) in the water sample? Describe the hardness level of the water using the U.S. government standards. 1a2 x0.01a-.0.156 165.imo1_ 0 1568 mo 25.I0 L M ‘.0'e al aA+ 006a1 a moL : Ca2 molarity Caco, concentration, mg/L 621.2 mal hardness level 167Explanation / Answer
Q1
EDTA + Ca+2 = EDTACa
mmol of EDTA = MV = 0.0128*12.25 = 0.1568 mmol of EDTA
mmol fo Ca+2 = 0.1568 mmol
V = 25 mL
[Ca+2] = mol/V= 0.1568/25 = 0.006272 M of Ca+2
b)
CaCO3 --> from cA
[CaCO3] = [Ca+] =) 0.006272
mass = mol*MW = (0.006272)(100) = 0.6272 g/L = 627.2 mg of CaCO3/L
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