An industrial process neutralizes acidic waste containing hydrochloric acid (HCl\text{HCl}HCl) by reacting it with solid calcium carbonate (CaCO3\text{CaCO}_3CaCO3). To prevent a runaway exothermic reaction and excessive foaming, engineers must decrease the rate of this heterogeneous reaction. Which of the following process modifications would achieve this?
Pulverizing the solid CaCO3\text{CaCO}_3CaCO3 into a fine powder before it enters the reactor bed.
Decreasing the concentration of the aqueous hydrogen ions by diluting the waste stream with recycled neutral water.
Pre-heating the incoming acidic waste stream using a process heat exchanger.
Increasing the total pressure of the reactor headspace by introducing pressurized nitrogen gas.
31 exam-style questions on OCR GCSE Chemistry Controlling reactions. Each one has a worked solution and a mark scheme showing where the marks go.