The Softening of Hard Water and Complexometric Titrations: An Undergraduate Experiment
Helena Ceretti, Enrique A. Hughes, and Anita Zalts
Universidad Nacional de General Sarmiento, Instituto de Ciencias - Área Química, Roca 850, 1663 San Miguel, Prov. Bs. As., Argentina
A 2-hour experiment for undergraduates is presented in which (i) water hardness is explained and demonstrated; (ii) ion-exchange resin properties are visually demonstrated and then used for softening water; (iii) complexometric titrations are used for evaluating water hardness before and after softening; and (iv) acid-base titration can be used to show that the Ca/Mg ions removed by the ion exchanger are replaced by H ions.
Supplement
A student handout, instructor notes, and suggestions for alternative/complementary procedures are provided.
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