9.3 - Estimation of Total Hardness using Ethylenediaminetetraacetic Acid (Leaving Cert Chemistry): Flashcards

$Ca^{2+}$ and $Mg^{2+}$ ions

Titration with EDTA solution

Eriochrome Black T

Wine-red to blue

0.01 M

pH 10

50 cm³

2-3 cm³

0.03 g

Deep wine-red

1:1 ratio

Maintain pH 10 for stable complexes with $Ca^{2+}$ & $Mg^{2+}$

Overestimate total hardness

Boil water first, then titrate with EDTA

ppm of $CaCO_3$