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 6 2+ 𝑎𝑞 +𝑆 𝑂 4 2− (aq)

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

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 6 2+

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

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

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

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 1.00 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

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 ×249.59 𝑔 𝑚𝑜𝑙 𝑑 𝑠𝑎𝑡 × 1000𝑚𝐿 1𝐿 = 𝐶𝑢 2+ 𝑠𝑎𝑡 ×249.59 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