Project ForgeAn autocatalytic liquid phase reaction, A+R→2R, is conducted in an isothermal batch reactor with a small initial concentration of R. The order of reaction with respect to both reactants is positive. The rate of reaction (−rA) versus concentration, CA, as the reaction proceeds, is depicted by
- a curve rising from near-zero at high CA to a peak at intermediate CA, then falling back toward zero as CA→0 (bell/hump shape)
- Ba straight line decreasing linearly from high CA to low CA
- Ca straight line increasing linearly from low CA to high CA
- Da constant, flat line independent of CA
Explanation
For autocatalytic kinetics −rA=k·CA·CR, the rate depends on the product of both concentrations. Starting at CA=CA0 with R nearly absent, the rate is low (little R to catalyze). As the reaction proceeds, CR builds up (autocatalytic acceleration) even as CA falls, driving the rate to a maximum at some intermediate CA. As CA→0 near completion, the rate falls back toward zero despite abundant R — producing the characteristic bell-shaped curve.
Source: GATE CH 2010 (2010)
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