Determining the Percent Amount of Nickel Present in an Unknown Substance

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Introduction: Determining the percent amount of nickel present in an unknown substance The purpose for this experiment was to determine the percent composition of nickel in an unknown substance using quantitative analysis. Quantitative analysis is a division of analytical chemistry which allows people to deduce how much of a substance is present in a given sample. Analytical chemistry is an important area in science as it enables scientists and researchers to discover whether substances—that have the potential to be harmful to people or the environment—exist in otherwise safe or healthy conditions. Procedure For this experiment .200 grams of solid unknown nickel compound “C” was measured out on a scale and then dissolved in 20mL or deionized water. When the compound had completely dissolved, 4-5 drops of ammonium hydroxide (NH4OH) was added to the solution in order to create a precipitate. As the NH4OH was added the solution became cloudy. Slowly 25mL of dimethylglyoxime (C4H8N2O2 or DMG) was added to the solution while stirring. As soon as the DMG was added it immediately turned pink and formed the Ni(DMG)2 precipitate. Below is the reaction equation for this. 2 C4H7N2O2- + Ni2+ → Ni(C4H7N2O2)2 Next a piece of filter paper was weighed by itself as well as an empty plastic boat. The filter paper was then wetted with deionized water and placed in the Buchner funnel and assembled to a side-arm vacuum flask which was then connected to a vacuum filter. The pink precipitate was then poured slowly into the center of the funnel—any leftover precipitate left in the beaker or on the stirring rod was rinsed with deionized water and poured into the funnel. The funnel collected cloudy pink filtrate which then needed to be filtered two more times until the filtrate came out clear. Once all the precipitate had been collected on the filter paper it was

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