Question

An EDTA solution is standardized against a solution of primary standard CaCO3 (0.5622 g dissolve in 1000 ml of solution) and titrating aliquots of it with the EDTA. If a 25.00 ml aliquot required 21.88 ml of the EDTA, what is the concentration of the EDTA?

Answer 1

mols CaCO3 = grams/molar mass
M CaCO3 = mols/L
mol = 0.5622/100 = 0.005622 and that is in 1L; therefore M = 0.005622M.
Then I would use
MEDTA x 21.88mL EDTA = MCaCO3 x 25.00 mL CaCO3. Solve for MEDTA

Answer 2

first get for the moles of CaCO3
mols CaCO3= 0.5662g*(1mol CaCO3/100gCaCO3)
Molarity of CaCO3= mols CaCO3/L of solution
=0.005622mols/1L
M EDTA= [(molarity CaCO3)(mL aliquot)]/
mL of EDTA
M EDTA= [(0.005622)(25)]/21.88
= 0.00642 M