1. 𝐶𝑢 𝐻 2 𝑂 5 𝑆 𝑂 4 2− 𝑠 + 𝐻 2 𝑂 l ⇄ 𝐶𝑢 𝐻 2 𝑂 6 2+ 𝑎𝑞 +𝑆 𝑂 4 2− (aq)
Determination of the Solubility of Cu(H2O)5.SO4(s) at 0oC using spectroscopy
𝐶𝑢 𝐻 2 𝑂 5 𝑆 𝑂 4 2− 𝑠 + 𝐻 2 𝑂 l ⇄ 𝐶𝑢 𝐻 2 𝑂 𝑎𝑞 +𝑆 𝑂 4 2− (aq)

2. Beer’s Law 𝐴=𝜀∙𝑙∙ 𝐶𝑢 2+ Absorbance Path Length
“The stronger the brew, the less light that goes through”
Absorbance
𝐴=𝜀∙𝑙∙ 𝐶𝑢 2+
Molar Extinction Coefficient
Path Length
𝐴= log 𝐼 0 𝐼 𝑡

3. Beer’s Law 𝐴= 𝜀𝑙 𝐶𝑢 2+ = m 𝐶𝑢 2+
If we know εl = m we can measure the concentration by measuring the absorbance
We can do this by calibrating the spectrometer, by measuring the absorbance at known concentrations of [Cu2+]
The slope of the calibration curve is ε.l = m
𝐶𝑢 𝐻 2 𝑂

4. Part A: Calibrating the Spectrometer
Flask #
0.200 M CuSO4(mL)
H2O
(mL)
[Cu2+]
(mol/L)
Absorbance 1
0.00
5.00
0.000 2
1.00
4.00 3
2.00
3.00 4 5 6
0.200
𝐶𝑢 2+ = 𝑉 𝐶𝑢 (𝑚𝐿)×0.200𝑀 5.00𝑚𝐿
Pipette or use a burette to dispense the reactants into a small test tube

5. Part A: Calibrating the Spectrometer
Calibrate the SpectroVis spectrometer with distilled H2O filling a cuvette
Measure the absorbance spectrum of CuSO4(aq)
Identify the wavelength of maximum absorption lmax
Conduct an Absorbance vs. Concentration experiment on the SpectroVis by selecting and choosing Abs vs Concentration
Get slope of A vs. [Cu2+] curve = m

6. Part B: Measuring the Absorbance of the saturated solution at 0oC
Take about 1.8 g of Cu(H2O)5.SO4(s) in a small test tube
Add about 3 ml of DI H2O
Place in ice bath and cool to 0oC
Pipette 1.00 mL of the saturated solution into a new test tube
Pipette 4.00 mL DI water into the same tube
Measure the absorbance at lmax
Determine [Cu2+]dil
Determine [Cu2+]sat
Determine Solubility of CuSO4.5H2O per 100g H2O at 0oC

7. Sample Calculations Determining [Cu2+]sat
1.00 mL of the saturated solution are diluted in 4.00 mL of DI water so
[Cu2+]dil = [Cu2+]sat× 1.00 𝑚𝐿 𝑚𝐿+4.00 𝑚𝐿 =0.2×[Cu2+]sat
[Cu2+]dil = 𝐴𝑏𝑠𝑜𝑟𝑏𝑎𝑛𝑐𝑒 𝑠𝑙𝑜𝑝𝑒 𝑜𝑓 𝑐𝑎𝑙𝑖𝑏𝑟𝑎𝑡𝑖𝑜𝑛 𝑐𝑢𝑟𝑣𝑒
And
[Cu2+]sat=5× [Cu2+]dil = 5×𝐴𝑏𝑠𝑜𝑟𝑏𝑎𝑛𝑐𝑒 𝑠𝑙𝑜𝑝𝑒 𝑜𝑓 𝑐𝑎𝑙𝑖𝑏𝑟𝑎𝑡𝑖𝑜𝑛 𝑐𝑢𝑟𝑣𝑒

8. Sample Calculations
Determining the solubility from [Cu2+]sat and the density dsat
𝑑 𝑠𝑎𝑡 × 1000𝑚𝐿 1𝐿 = 𝑚 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 1𝐿 = 𝑚 𝐶𝑢𝑆 𝑂 4 + 𝑚 𝐻 2 𝑂 1𝐿
𝑚 𝐶𝑢𝑆 𝑂 4 = 𝐶𝑢 2+ 𝑠𝑎𝑡 × 𝑔 𝑚𝑜𝑙
𝑑 𝑠𝑎𝑡 × 1000𝑚𝐿 1𝐿 = 𝐶𝑢 2+ 𝑠𝑎𝑡 × 𝑔 𝑚𝑜𝑙 + 𝑚 𝐻 2 𝑂 1𝐿
𝑚 𝐻 2 𝑂 = 𝑑 𝑠𝑎𝑡 × 1000𝑚𝐿 -
Solubility per 100g H2O = 𝑚 𝐶𝑢𝑆 𝑂 4 𝑚 𝐻 2 𝑂 ×100𝑔 𝐻 2 𝑂