Wednesday, July 20, 2011

Equilibrium in Chemical Processes

Decomposition of Calcium Carbonate
Calcium carbonate when heated to 1073K in a closed evacuated vessel, starts decomposing to yield calcium oxide and carbon dioxide gas. Carbon dioxide builds up pressure within the vessel which can be recorded on a manometer. The pressure goes on increasing as the reaction proceeds and finally becomes constant. It appears as if the reaction has come to a stop although CaCO3 is still present. This indicates that the system has attained the equilibrium state.
At equilibrium, rate of forward reaction i.e.
CaCO3     CaO  +   CO2
becomes equal to rate of  backward reaction i.e.
CaO   +   CO2    CaCO3
CaCO3        CaO  +  CO2  

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