Experimental Determination of Mass Percent Record all mass measurements. Report

Question

Experimental Determination of Mass Percent Record all mass measurements. Report the mass of double salt used. The beaker weighs 45.131 g; the beaker and double salt weigh 45.529 g; the double salt weighs 0.398 g. The beaker weighs 49.927 g; the beaker and double salt weigh 50.381 g. Record the absorbance of the double salt solution: 0.513 0.310 Determine and report the Cu^2+ concentration in the double salt solution from the measured absorbance and the calibration curve either graphically or from the regression line equation (Excel only) as described in TREATMENT OF DATA. Illustrate (graphical) or show (regression line) your work on the graph, and record the result here: The regression line from Excel is y = 0.314x + 0.0028. The cu^2+ concentration is 1.621 mg/mL. Determine the mass of copper in the double salt solution using the found Cu^2+ concentration and the volume of the prepared double salt solution. 81.05 mg (0.08105 g) Determine the mass percent of copper in the double salt from the found mass of copper and the mass of the double salt sample. 20.4% Formula: K_2Cu_2(SO_4)_3(H_2O) Calculate the formula of the double sulfate from your data in terms of w, x, y, and z in the general formula: K_ Cu_ (SO_4)_ (H_2O)_2 Show your set-ups.

Explanation / Answer

KwCux(SO4)y(H2O)z

w=12.6%

x=20.4%

y=46.66%

z=20.2%

ratio of composition =0.126:0.204:0.4666:0.202

dividing by the smallest no- 1:1.62:3.7:1.6

or rounding off the decimals to nearest integers,

required ratio=1:2:4:2

formula=KCu2(SO4)4 .2 H2O

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