Hard water cor tons Ca^2+. Mg^2+ and Fe^2+. which interfere with the action of s

Question

Hard water cor tons Ca^2+. Mg^2+ and Fe^2+. which interfere with the action of soap and leave an insoluble coating on the insides of containers and ppes when heated. Water softeners replace these ions with Na+. Koep in mind that charge balance must be maintained. K 1300 L of hard water contains 0.024 M Ca^2+ and 0.0040 M Mg^2+. how many moles of Na+ is these ions? Express your answer using two significant figures. If the sodium is added to the water softener in the term of NttCI. how many grams of sodium chloride are needed? Express your answer using two significant figures.

Explanation / Answer

part A )

moles of Ca+2 = molarity x volume

                        = 0.024 x 1300

                         = 31.2

moles of Na+ are need for Ca+2 = 2 x 31.2 = 62.4

moles of Mg+2 = 0.004 x 1300

                          = 5.2

moles of Na+ are need to replace = 2 x 5.2 = 10.4

total Na+ moles needed = 62.4 + 10.4 = 72.8

moles of Na+ = 73

part B)

moles of NaCl = 73

molar mass of NaCl = 58.5

mass = moles x molar mass

          = 73 x 58.5

         =4258.8

        = 4.3 x 10^3 g

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