Unformatted text preview: (2*(116.12 ‐ 1)+58.69)/58.69*0.02g = 98.5 mg. (one proton is removed from DMG in complexing the Ni 2+ ion). This is enough that weighing precision should be adequate at the 1% level, but questionable at the 0.1% level. For EDTA titration, if the EDTA is ~ 0.02 M, titration volume would be 3.4×10 ‐ 4 mol/2×10 ‐ 2 mol L ‐ 1 = 1.7×10 ‐ 2 L = 17 mL, about what one would desire. Further, Mg 2+ would interfere with the EDTA titration. Thus, gravimetry is the preferred method. 3. If you had a solution that was to be used to generate the unknown for this lab, why would you NOT use the spectrophotometric method to assay the solution? 1 point. The spectrophotometric method requires a standard solution for calibration. One can't standardize with the solution that is being prepared to be the standard! Useful data: atomic weight of Ni: 58.69. Molecular weight of DMG (neutral molecule): 116.12....
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- Fall '08
- Mole, 1%, 0.1%, 2 L, 2 mg, mol/2×10‐2 mol L‐1