In the case of , CaCO3s⇌CaOs+CO2g, attainment of equilibrium state is noticed with the help of constancy in

If the reaction vessel is connected to a manometer the pressure increases due to the liberation of CO2 gas.. At equilibrium state where rate of formation of CaOs & CO2g from CaCO3s is equal to the their conversion back to CaCO3s, contsancy in manometer reading is observed.CaO,CaCO3 are solids their concentraitons practically remain unchanged during the processSince all the species involved are colourless, colour is not useful to identify equilibrium state;