plz help~ Can calcite (CaCO_3(s)) coexist with lime (CaO(s)) in contact with the

Question

plz help~

Can calcite (CaCO_3(s)) coexist with lime (CaO(s)) in contact with the atmosphere? (i) Calculate the Gibbs energy for the following reaction: CaCO_3(s) = CaO(s) + CO_2(g) (ii) Derive an equilibrium constant for the reaction from the Gibbs energy (use data from your text or from Woods and Garrels et al. (1987). Be careful about units, (kcal notequalto kJoule). (iii) Compare the equilibrium partial pressure of CO_2(g) with the atmospheric partial pressure of CO_2, p(CO_2), equal to 10^-3.5 atmospheres. Assume that the solids have unit activity. Which way does the reaction go?

Explanation / Answer

for the reaction CaCO3(s)----->CaO(s)+ CO2(g)

Standard gibbs free energy= deltaGf(CO2)*1 + deltaGf(CaO)- deltaGf(CaCO3)= -603.54-394.38+1127.8 = 129.88 Kj

gibbs free eenrgy change and Equilibrium constant are related as

deltaGf= -RTlnK, K= equilibrium constant

lnK= -detlaG/RT = -129.88*1000/(8.314*298), K= 1.711*10-23

but K= PCO2= 1.711*10-23 atm. This is less than the partial pressure of CO2 in the atmosphere.

The reaction proceeds from atmosphere into CO2.

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