Cyclic voltammetry was used to measure the peak current at several different scan rates for the reversible reaction Sn(IV) → Sn(II) of an organic tin-containing complex. The concentration of the reactant is 4.96 mM and the area of the working electrode is 0.0250 cm². Calculate the diffusion coefficient of the reactant for this two-electron reduction. Scan Rate (V/s) 0.0135 0.0279 0.0538 0.0951 0.149 0.201 0.274 Peak Cathodic Current (μA) 4.12 5.48 7.70 9.87 12.52 14.91 17.59

The Eºc cell Ecell = 0.135 V for the reaction 312(s) + 5Cr₂O7²-(aq) + 34H*(aq) →→ 6103¯(aq) + 10Cr³+ (aq) + 17H₂O What is Ecell if [Cr₂O7²-] = 0.036 M, [H*] = 0.28 M, [103] = 0.00027 M, and [Cr³+] = 0.0015 M? V

Calibration of a glass electrode gave a reading of 139.3 mV with a 0.05 m potassium hydrogen phthalate buffer standard ( pH = 4.015), and a reading of -160.7 mV with a 0.01 m borax buffer standard (pH = 9.139), both measured at 30 °C. What is the observed slope (mV/pH unit) of the calibration curve? slope observed What is the theoretical slope at 30 °C? = slope theoretical pH : What is the pH of an unknown that gives a reading of 42.5 mV with this electrode at 30 °C? = = mV/pH mV/pH

Calculate the cell potential (in V) of the following cell with transference at 25°C: Pb(s) PbSO4(s), CuSO4(m = 0.2, y = 0.110) CuSO4(m = 0.02, y = 0.320), PbSO4(s) Pb(s) The transport number of Cu²+ is 0.370. Express your answer in three significant figures.