Only answer #4 Suppose you have a copper nitrate solid. You are not sure, howeve
ID: 718615 • Letter: O
Question
Only answer #4Suppose you have a copper nitrate solid. You are not sure, however, if the solid is copper (I) nitrate, CuNO3, or copper (II) nitrate, Cu(NO3)2. You dissolve a 0.1015 gram sample of this solid in water and nitric acid and then dilute it to a final volume of 100. mL. You treat a sample of this solution with ammonia and then measure the absorbance of the resulting blue-violet solution. By comparing the absorbance of this solution to that of standard copper solutions you determine the concentration of Cu2+ to be 5.41 x 10-3 M. Use this information (and the hints below) to find the mole ratio of Cu : NO3 and determine the chemical formula for the original copper nitrate sample.
4) Determine the moles of NO3 present in the solid sample.
Explanation / Answer
If Cu2+ was determined to be 0.00541M you multiply by 0.1L (100 mL) to find that there are 0.000541 mol of Cu in solution. Multiplying moles by molecular mass (63.546) tells you that the mass of copper in solution was 0.03438 g.
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