2. Calcium and carbon dioxide combine spontaneously @ 298 K under standard state

Question

2. Calcium and carbon dioxide combine spontaneously @ 298 K under standard state conditions (P CO2 = 1atm) to produce calcium carbonate.

CaO (s) + CO2 (g) ---> CaCo3 (s)

a) Based on the reaction stoichiometry and the phases of the reactants and products, is the entropy change for this reaction ( delta S degree rx) negative or positive? Explain your answer.

b) Is the reaction exothermic or endothermic? Briefly justify your answer using an equation in your response.

c) Should the temperature be raised or lowered in order to make the reaction non-spontaneous under standard state conditions (P CO2 = 1 atm)? Briefly explai your answer.

3. a)For the reaction KCl (s) ---> KCl (aq), state whether the entropy of te system increases or decreases. Explain your reasoning.

b) The temperature of the solution is slightly lower after 1 mole of KCl dissolves. What does this fact indicate about the enthalpy of this process?

4. Thermodynamic data for C(graphite) and C (diamond) at 298 K is given in the table below.

a) Calculate delta Hdegree and delta Sdegree and delta Gdegree for the transformation of one mole pf graphite to diamond at 298K.

b) Is there a temperature at which this transformation will occur spontaneously at atmospheric pressure? Justify your answer.

Explanation / Answer

2.a) For the reaction, the entopy will be decresed, because entropy is a measure randomness. In the reaction the reactants are solid and gas , but the product is in solid phase. So, for the given reaction delta S is negative, due to decrease in entropy.

b) The reaction is exothermic, because the reactants are in the phase of solid and gas and product formed is a solid. When gaseous phase reactant (CO2) forms solid, heat is released.

c) Since the reaction is exothermic,releases heat. According to Le chatlear principle, if the temperature is less for the system the reaction move toword product and maintains the equilibrium, but if the temperature is raised the reaction will not be forwarded. It facilitates the backword reaction. So the reaction becomes non-spontaneous.

3. a) In solid KCl, the ions are in partilar crystal structure and packed in a manner. Once it is dissolved in water, the ions dissocate and they will be movment. Therefore the entropy of the system is increses.   

b) If the temperature of the system decreses means the heat is liberated out. At this point, the enthalpy of the system is less compared to initial. Therfore the delta H of the system is negative.

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