9-21 A kinetics study was performed to examine the rate-controlling steps in a gas-solid reaction governed by the shrinking-core model: A(g) + 2B(s) products(s, g) Experiments were conducted with four different sizes of nonporous spherical particles with the temperature and partial pressure of A kept constant at 700 K and 200 kPa, respectively. The time to complete reaction, f, was measured in each case, and the following data were obtained, with PBM = 2.0 x 105 mol m-: particle radius/m: 0.005 10-5t/s: 2.31 0.010 0.015 0.020 4.92 7.83 11.0 In a separate set of experiments, it was determined that the gas-film mass transfer coefficient (kAg) was 9.2 x 10-5 s-. (a) Determine the rate constant for the intrinsic surface reaction (kas/m s-) and the effective ash-layer diffusion coefficient for A (D/m s). (b) Is one process clearly rate limiting? Justify your answer. (c) Determine the time required for 80% conversion of a 0.010 m particle, given the same flow conditions, T, and PA used in the kinetics experiments