4) Distilled water (2.194 mL) is added to a cuvette for calibration of the Spect

Question

4) Distilled water (2.194 mL) is added to a cuvette for calibration of the SpectroVis. 3 aliquots, each 223.012 µL in volume, of 0.40 M CuSO4 are then added sequentially to the water in the cuvette. What is [CuSO4] after the third aliquot is added? Provide your response to three digits after the decimal.

5) The reported molar absorptivity of CuSO4 is 0.76 L mol-1 cm-1. If a solution of CuSO4displays an absorbance of 0.054 in a cuvette that is 0.615 cm in length, what is the concentration of the CuSO4 solution? Report your response to three digits after the decimal. _____ M

Explanation / Answer

4)

Total volume of aliquots = 3*0.000223012ml = 0.000669036ml

No of mole of CuSO4 =(0.40mol/1000ml)*0.000669036ml = 2.68*10-7 mol

volume of water = 2.194ml + 0.000669036ml = 2.194669

[CuSO4]=( 2.68*10-7 mol/2.194669ml)*1000ml =1.221*10-4M

5) Absorbance = Molar absorptivity * path length * Concentration

Concentration = Absorbance /(Molar absorptivity * path length)

= 0.054 /0.76(L/mol) *cm-1 * 0.615cm

= 0.116M

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