The amount of nickel (II) in a steel sample can be determined by the following p

Question

The amount of nickel (II) in a steel sample can be determined by the following procedure: " Weight 25mg of sample into a 400-mL beaker, and dissolve by warming with 50mL of 6M HC1. Carefully, introduce 15mL of 6M HNO_3, and boil gently to expel the oxides of nitrogen. Dilute with water the resulting solution to 200mL, and heat nearly to boiling. Introduce 30mL of 25% tartaric acid, and neutralize with 3mL of concentrated NH_3. Heat to 60 to 80degreeC and add 20mL of a 1% (w/v) alcoholic solution of dimethylglyoxime. Stirring, introduce 5mL of 6M HNO3. Digest for 60min at 60degreeC, cool for at least lhr, and filter. Transfer the liquid solution to a 50mL volumetric flask. Add 5mL of complexing agent (diethanoldithiocarbamate), complete with water to the mark and measure the absorbance of the liquid solution at 638nm." Answer the following questions: 1) Describe the preparation of the blank. 0.5 points 2) Assume you are determining the concentration of nickel via the calibration curve method. You know that co alt (II) remains in the analytical sample and it forms a complex with diethanoldithiocarbamate. The concentration of cobalt (II) in the resulting liquid solution is 20mg.mL^-1. No other interference exists in the analytical sample. Describe the experimental procedure for the preparation of standards.

Explanation / Answer

1) First of all you should know that blank are all the " ingredients" of the reaction unless the analyte and that all steps are done. Thus blank is prepared as follows:

"in a beaker of 400mL, add 50mL of 6M HCl, introduce 15mL of 6M HNO3 and boil gently. Dilute with water the resulting solution to 200mL, and heat nearly to boiling. Introduce 30mL of 25% tartaric acid, and neutralize with 3mL of concentrated NH3. Heat to 60 to 80 ºC and add 20mL of a 1% (w/v) alcoholic solution of dimethylglyoxime. Stirring, introduce 5mL of 6M HNO3. Digest for 60min at 60ºC, cool for at least 1hr, and filter. Transfer the liquid solution to a 50mL volumetric flask. Add 5mL of complexing agent (diethanoldithiocarbamate), complete with water to the mark and measure the absorbance of the liquid solution at 638nm"

2) The solution is prepared using a primary standard nickel. An amount of primary standard is carefully weighed ( analytical balance), dissolved in the appropriate solvent and diluted to a known volume accurately in a volumetric flask and then makes all the treatment was made to the sample and must preparing a cobalt standard in order to determine interference of cobalt in the sample and subtract the final outcome to determine the amount of nickel (II) in a steel sample.

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