A 50 mm (diameter) sphere of solid nickel is oxidized in a gas mixture containing 60% argon and 40% oxygen by volume. The rate of oxidation of nickel is controlled by the rate of transport of oxygen through the concentration boundary layer. The rate of oxidation (in moles of nickel per minute (mol / min), rounded off to two decimal places) is _______.
Given: Total pressure = 1 atm.; Temperature = 1173 K; Concentration of oxygen at the surface of the solid = 0; Boundary layer mass transfer coefficient = 0.03 m⋅s⁻¹; Universal gas constant, R = 8.205 × 10⁻⁵ m³⋅atm⋅K⁻¹⋅mol⁻¹; Assume ideal gas behavior.