In the titration of 25.00 ml of a water sample, it took 19.790 ml of 3.630x10-3
ID: 602845 • Letter: I
Question
In the titration of 25.00 ml of a water sample, it took 19.790 ml of 3.630x10-3 M EDTA solution to reach the endpoint. Complete the questions below:The total hardness is due to one or a combination of Ca2+, Mg2+, and Fe2+ in your sample. It is convenient to express this hardness as though it was entirely due to Ca2+. Making this assumption, determine the number of moles of Ca2+ present in the bottled water sample titrated. (enter your answer with 3 significant figures)
Explanation / Answer
Ca2+ + EDTA4-----> Ca2EDTA. Normally ethylenediaminetetraacetic acid(EDTA) remains in solution as EDTA4- ions and therefore 2Ca2+ ions are needed for total precipitation. for each mol of EDTA,2 mols of Ca2+ ions are needed. EDTA needed for titration: 19.79*3.63*10^-3 mmols. so,Ca2+ ions present was: (2*19.79*3.63)*10^-3 mmols= 1.43675*10^-4 mols.