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# Enthalpy- kinetically unstable?

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1. 'A mixture of calcium oxide and carbon dioxide is kinetically unstable with respect to calcium carbonate. What would happen if you passed carbon dioxide through a tube containing solid calcium oxide? If you think a reaction might occur, how much heat would be absorbed or evolved during the reaction?'

I'm really confused on how to answer this, i not really sure what kinetically unstable means. I think kinetically stable means that at ordinary temperature nothing happens because the activation energy is too high so does kinetically unstable mean the opposite? That at ordinary temperature a reaction occurs because the activation energy is low?

2. Hi Lummzie,
I think this question is a twist on the thermal decomposition of CaCO3. Firstly, when a reaction is said to be kinetically unstable, it means it will happen relatively fast. (As a quick rule of thumb: Kinetics = Speed of reaction, Thermodynamics = Energy of reactant/product materials)

How much heat would be absorbed/evolved during the reaction?

Well, if you think of the equation CaCO3(aq) > CaO(aq) + CO2(g),
heat is needed to break the bonds in CaCO3, so the reaction is said to be endothermic (takes heat from surroundings). The reaction given to us is the exact opposite, meaning the exact opposite will happen in terms of energy as well. Heat will be given off, and thus the reaction is said to be exothermic. I am unsure whether you are required to give a rough guess at what the energy would be although I think that would be a bit mean. You could just say that the enthalpy change will be negative. Hope this helps!

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