identify whether entropy increases or decreases for each of the following changes. CaCO3 (s) = CaO (s) + CO2 (g) (give 2 reasons)?
- pisgahchemistLv 77 months ago
CaCO3 decomposition ......
A rotary lime kiln heats limestone (CaCO3) at a high temperature where it decomposes to calcium oxide (lime) and emits carbon dioxide gas.
CaCO3(s) --> CaO(s) + CO2(g) ................ ΔH is positive (endothermic)
Since heat must be added, the reaction is endothermic and ΔH is positive. The decomposition produces a gas as well as a solid, so that tells us that entropy is increasing, so ΔS is positive. Gaseous molecules exist in more microstates than do solids.
You can always calculate ΔS. That makes for a good reason.
ΔS = ΣS(products) - ΣS(reactants)
ΔS = S(CaO) + S(CO2) - S(CaCO3)
ΔS = 39.8 J/molK + 213.7 J/molK - 92.9 J/molK = 160.6 J/molK .... or .... 0.1606 kJ/molK ............... ΔS is positive
* entropy values from https://www.chem.wisc.edu/deptfiles/genchem/netori...