3) (a) A lab student analyzed her nickel-en complex for ethylenediamine, en, con

Question

3) (a) A lab student analyzed her nickel-en complex for ethylenediamine, en, content. A 0.507 g sample of the synthesized Ni-en complex was dissolved in about 50 mL of water and titrated with 0.161 M HCl . Endpoint required 38.18 mL of the HCl . What is the mass (in grams) of en in the Ni-en complex analyzed?

(b) Continuing on with the analysis of the Ni-en complex as found in question (a), 40 mL of dimethylglyoxime, DMG, solution was added to the titrated nickel-en complex solution. The resulting beautiful red complex, Ni(DMG)2 was collected by filtration and found to weigh 0.487 g. What is the mass (in grams) of Ni in the Ni-en complex analyzed?

(c) Determine the empirical formula of the complex synthesized in questions (a) and (b) above.

Explanation / Answer

3) analysis of sample

(a) moles of HCl used = 0.161 M x 38.18 ml = 6.15 mmol

moles of EDTA = 6.15/4 = 1.54 mmol

mass of en in the complex = 1.54 x 292.24/1000 = 0.449 g

(b) moles of Ni(DMG)2 = 0.487/290.933 = 0.0017 mol

moles of Ni = 0.0017/2 = 0.00085 mol

mass of Ni in complex = 0.00085 x 58.69 = 0.050 g

(c) Empricial formula in (a) Ni-en

empirical formula in (b) Ni(DMG)2

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