EDTA – An Introduction CHM 103 Sinex

EDTA is ethylenediaminetetraacetic aicd For more information on EDTA – see the MOTM for March 2004.MOTM for March 2004 Six binding sites 4 H on carboxylic acid groups (H’s are removed, so –COO - ) 2 lone pairs of electrons on nitrogens EDTA Chime structure

Fe +3 + EDTA -4  FeEDTA -1 1:1 metal ion to EDTA metal ion with octahedral geometry

chemistry Ca +2 with EDTA – 1:1 at equivalence point: moles Ca = moles EDTA so to find moles: moles = M x V L standard calcium solution from CaCO 3 CaCO 3 (s) + 2HCl(aq)  CaCl 2 (aq) + CO 2 (g) + H 2 O indicator – MgIn - HIn -2 wine red sky blue After Ca +2 reacts with EDTA, EDTA complexes Mg +2 from indicator.

indicator Tracking the metal ion - EDTA titration

If a student masses out g calcium carbonate, dissolves it in HCl, and then places it into a mL volumetric flask, what is the molarity of the calcium ion? g x 1 mole/100g = x moles Ca x moles Ca +2 /0.5000L = M answer If mL of the Ca +2 solution above requires mL of EDTA to titrate, what is the molarity of the EDTA? M Ca x V Ca = M EDTA x V EDTA hint