CFD is adopted to predict the effects of mixing during batch-wise gas-liquid reactive precipitation. A 2-D flow simulation is developed for the chemical reaction with precipitation process using the moment transformation of the population balance. A comparison is made between the CFD model predictions and the film and penetration theories, respectively, for the same time range using the calcium carbonate system. The CFD simulation demonstrates an intermediate behaviour in predicting the transient mean crystal size highlighting the role of the hydrodynamics in the precipitation process.