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Unformatted text preview: Subtract the amount in excess by the amount started with to find the amount of EDTA used M(Ca 2+ ) = .03 [mol / L] V avg (Ca 2+ ) = (8.19 + 7.38 +7.42) / 3 = .00766 L Moles(Ca 2+ ) = .03 x .00766 Moles(Ca 2+ ) = 2.3 x 104 mol Excess Moles EDTA = 2.3 x 104 mol Moles EDTA = 2.8 x 104 2.3 x 104 Moles EDTA = .00005 mol The next step is to find the amount, in milligrams, of calcium that are in the calcium. Multiplying the number of moles by the molar mass will give us the answer in the grams. In order to convert to milligrams, we must multiply the mass by 1000. Moles(Ca 2+ ) = .00005 mol Mass(Ca 2+ ) = (.00005) x (40.078) Molar Mass (Ca) = 40.078 g Mass(Ca 2+ ) = .002 g = 2 mg Since there are 2 mg of calcium in 2.5 ml of Deans 2% milk, then there must be .8 mg in 1.0 ml of Deans 2% milk....
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 Spring '08
 jursich
 Molarity

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