Assignment 3

A chronoamperometry experiment is performed at a planar electrode (one-electron transfer reaction) with an area of 0.50 cm² in a solution (diffusion coefficient of analyte = 1.2 × 10⁻⁵ cm²/s, bulk concentration of analyte  = 0.01 M). Immediately after a potential step, the current follows the Cottrell behaviour. Calculate the faradaic current (in mA) at t = 10 ms.

Mathematical Equivalence

ON

In a diffusion-limited chronoamperometry experiment, the current at t = 5 ms is 2.0 mA. Assuming Cottrell behaviour, when will the current decay to 1.0 mA (in ms)?

Mathematical Equivalence

ON

In a heavy-metal detection assay, Pb²⁺ is reduced to Pb during a 30 s chronoamperometric deposition. If the total charge passed is 0.30 C, calculate the mass of Pb deposited (atomic weight of Pb = 207 g/mol) in mg. 

Mathematical Equivalence

ON

A chronoamperometry corrosion test on an iron electrode (area = 1.00 cm²) generates 2.72 C of charge over 60 s as iron dissolves to Fe²⁺. Given iron’s atomic weight of 55.85 g/mol and density of 7.87 g/cm³, determine the equivalent thickness (in µm) of iron corroded from the electrode, assuming corrosion happens uniformly on the surface.

Mathematical Equivalence

OFF

A chronoamperometric measurement at a 1.0 cm² electrode (n = 1) in a solution with D = 1.0 × 10⁻⁵ cm²/s produced a current of 50 μA at t = 1.0 s. Using the Cottrell equation, estimate the bulk concentration (in M) of the electroactive species in the solution. 

Mathematical Equivalence

ON

A Nyquist plot for an electrochemical system shows a single semicircular arc with a diameter of 150 Ω (intercept difference between high-frequency and low-frequency ends). What is the charge-transfer resistance R_ct indicated by this semicircle (in Ω)?

Mathematical Equivalence

ON

Consider a Randles cell (R_ct–C_dl in parallel, with a negligible solution resistance). If R_ct = 100 Ω and C_dl = 1.0 × 10⁻⁵ F, at what frequency (in Hz) will the Nyquist semicircle reach its peak (maximum –Z″)?

Mathematical Equivalence

ON

In a simple RC circuit, at the frequency where the capacitive impedance equals the resistance, what is the phase angle (°) of the total impedance?

Mathematical Equivalence

ON

A Nyquist plot shows a semicircle apex (maximum imaginary point) at 1.00 kHz. The diameter of this semicircle is 50 Ω. Determine the double-layer capacitance of the interface (in F). 

Mathematical Equivalence

ON

A Bode plot for a fuel cell exhibits a high-frequency intercept of 0.10 Ω (series resistance). If the cell delivers a current of 5.0 A, what magnitude of IR drop (in V) does this internal resistance cause?

Mathematical Equivalence

ON