1. EDTA – An Introduction
CHM 103
Sinex

2. 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.

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

4. 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.

5. Tracking the metal ion - EDTA titration
indicator

6. 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 10-3 moles Ca+2
5.251 x 10-3 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?
MCa x VCa = MEDTA x VEDTA
hint