A pulverized coal particle burns in pure oxygen at 1200°C. The process is limited by diffusion of the oxygen counterflow to the CO 2 formed at the particle surface. Assume that the coal is pure carbon...

A pulverized coal particle burns in pure oxygen at 1200°C. The process is limited by diffusion of the oxygen counterflow to the CO₂
formed at the particle surface. Assume that the coal is pure carbon and has an initial diameter of 0.01 cm. If D = 1.032
 10^–4
m²/s, calculate the time required for 90% of the carbon to burn away. What is the final diameter of the coal particle?