ENGW 1111 Lecture Notes - Lecture 11: Erlenmeyer Flask, Alkaline Earth Metal, Burette

• School: Northeastern University
• Department: English Writing
• Course: ENGW 1111
• Professor: Aaron S.Block

Document Summary

Estimation of the total hardness of a water sample using edta. Ethylenediaminetetraacetic acid (edta) is a reagent that forms edta-metal complexes with many metal ions (but not with alkali metal ions such as na+ and k+). In alkaline conditions (ph 9) it forms stable complexes with the alkaline earth metal ions ca2+ and. The edta reagent can be used to measure the total quantity of dissolved ca2+ and. Thus the total hardness of a water sample can be estimated by titration with a standard solution of edta. Suitable conditions for the titration are achieved by the addition of a buffer solution of ph 10. The buffer solution stabilises the ph at 10. There are h+ ions produced as the reaction proceeds, and without the buffer solution the ph would decrease. The edta reagent cannot under these conditions distinguish between the hardness caused by ca2+ and mg2+, or (directly) between temporary and permanent hardness.