Chapter 12: Problem 12
Find out whether it is possible to reduce \(\mathrm{MgO}\) using carbon at \(298 \mathrm{~K}\). If not, at what temperature it becomes spontaneous. For reaction, \(\mathrm{MgO}(s)+\mathrm{C}(s) \longrightarrow \mathrm{Mg}(s)+\mathrm{CO}(g), \Delta H^{\circ}=+491.18 \mathrm{~kJ} \mathrm{~mol}^{-1}\) and \(\Delta S^{0}=197.67 \mathrm{JK}^{-1} \mathrm{~mol}^{-1}\)
Short Answer
Step by step solution
Understanding the Gibbs Free Energy
Calculating Gibb's Free Energy at 298 K
Evaluate the spontaneity at 298 K
Find the Temperature for Spontaneity
Calculating the Temperature
Conclusion
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Spontaneity of Reactions
The exercise aimed at determining the spontaneity of reducing magnesium oxide (MgO) with carbon. The calculation of Gibbs Free Energy at standard conditions (298 K) with the given enthalpy (H^{0}) and entropy (S^{0}) values allowed us to assess whether the reaction is spontaneous at this temperature. By resolving the Gibbs formula with abla G = abla H - Tabla S, we can infer the spontaneity based on the sign of the resultant abla G.
Entropy and Enthalpy
Enthalpy, on the other hand, is a measure of the total energy of a thermodynamic system, including both internal energy and the energy required to displace its environment to make room for its volume. A positive change in enthalpy (abla H > 0) indicates that a reaction is endothermic, absorbing heat from its surroundings. Conversely, a negative abla H (< 0) signifies an exothermic reaction, where energy is released as heat to the surroundings.
The given exercise provides the values of both abla H and abla S for the reaction between magnesium oxide and carbon. By considering these values within the Gibbs Free Energy equation, we were able to calculate how they influence the reaction's spontaneity.
Chemical Equilibrium
The magnitude of the equilibrium constant (K_{eq}) provides insight into the position of equilibrium. A large K_{eq} value indicates a reaction that favors the formation of products, while a small K_{eq} value suggests a reaction favoring reactants. In the context of our exercise, by setting the Gibbs Free Energy equation to zero and solving for the temperature (T), we effectively find the temperature at which the system would reach equilibrium for the given reaction if it could achieve equilibrium at all.
Thermodynamics in Physical Chemistry
In our exercise, thermodynamics helps predict the conditions under which the reduction of MgO by carbon would spontaneously occur. By applying the equations and concepts of thermodynamics, such as the calculation of Gibbs Free Energy, we determined not only the spontaneous nature of the reaction at a given temperature but also the theoretical temperature at which the reaction would become spontaneous, based on the enthalpy and entropy values provided.
The exercise guides students to leverage these thermodynamics concepts to assess reaction spontaneity and equilibrium, enhancing their understanding of how energy and matter interact in chemical processes.