A jewelry pin with dimensions 4.0 cm × 1.0 cm (only the front face is exposed) is…
CHEMISTRY · Single correct · AP · Chemistry · Thermodynamics and Electrochemistry · Thermodynamics and Electrochemistry
Problem
A jewelry pin with dimensions 4.0 cm × 1.0 cm (only the front face is exposed) is first coated with a 5.0 µm barrier layer of nickel and then over-plated with gold until the COMBINED mass of deposited metals reaches 0.120 g. The current remains constant at 1.80 A throughout both steps.
Data:
• Ni²⁺, atomic mass 58.7 g mol⁻¹, density 8.90 g cm⁻³
• Au³⁺, atomic mass 197 g mol⁻¹, density 19.3 g cm⁻³
• Faraday constant = 9.65 × 10⁴ C mol⁻¹
Which of the following is closest to the total plating time?
(a) 232 s
(b) 120 s
(c) 98 s
(d) 88 s