This same EDTA solution was then used in a titration of a properly prepared solution representing the cement. Two milliliters of the cement solution (pH = 1.00) required 25.00 mL of the EDTA solution from part "A". At the end point, a very small amount of free Ca2+ could dissociate from the complex. What is that small molarity (M) of the free Ca2+ at the end point of the titration? The pK'f for this reaction at pH = 11.00 is 10.59.

• 3.27 x 10-8 M
• 8.93 x 10-8 M
• 1.88 x 10-7 M
• 3.19 x 10-7 M
• 4.21 x 10-7 M