EDTA – An Introduction CHM 103 Sinex

EDTA is ethylenediaminetetraacetic aicd 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 For more information on EDTA – see the MOTM for March 2004.

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 VL standard calcium solution from CaCO3 CaCO3(s) + 2HCl(aq) CaCl2(aq) + CO2(g) + H2O indicator – MgIn- HIn-2 wine red sky blue After Ca+2 reacts with EDTA, EDTA complexes Mg+2 from indicator.

Tracking the metal ion - EDTA titration indicator

If a student masses out 0.5251 g calcium carbonate, dissolves it in HCl, and then places it into a 500.0 mL volumetric flask, what is the molarity of the calcium ion? 0.5251 g x 1 mole/100g = 5.251 x 10-3 moles Ca+2 5.251 x 10-3 moles Ca+2/0.5000L = 0.1050 M answer If 25.00 mL of the Ca+2 solution above requires 18.93 mL of EDTA to titrate, what is the molarity of the EDTA? MCa x VCa = MEDTA x VEDTA hint