2 H2O (l) → 2 H2 (g) + O2 (g)
Using the thermodynamic values to calculate accurate values of ΔHr and ΔSr, will the reaction be product favored at high temperature? Why?
r stands for reaction
To determine whether the reaction is product-favored at high temperature, we need to consider the values of ΔHr (enthalpy change of the reaction) and ΔSr (entropy change of the reaction).
ΔHr reflects the heat energy change associated with a reaction. A negative ΔHr indicates an exothermic reaction, while a positive ΔHr indicates an endothermic reaction. In this case, the given reaction equation tells us that energy is released (exothermic) as two moles of water (liquid) are converted into two moles of hydrogen gas and one mole of oxygen gas. Since the reaction is exothermic, ΔHr will be negative.
On the other hand, ΔSr reflects the change in randomness or disorder of the system. A positive ΔSr indicates an increase in disorder, while a negative ΔSr indicates a decrease in disorder. In this reaction, two moles of water molecules are converted into three moles of gas molecules (two moles of H2 and one mole of O2). The conversion from a liquid to a gas generally increases the disorder, so ΔSr will be positive.
Now, let's consider the effect of temperature. According to the Gibbs Free Energy equation:
ΔG = ΔH - TΔS
Where ΔG is the change in Gibbs Free Energy, ΔH is the enthalpy change, T is temperature, and ΔS is the entropy change. At high temperatures, the term -TΔS becomes more significant.
If ΔG is negative, the reaction is product-favored, and if ΔG is positive, the reaction is reactant-favored. Since ΔHr is negative (exothermic), we know that ΔH will be negative. With a positive ΔSr and high temperature (T), the -TΔS term will dominate the equation, making it more negative. As a result, the ΔG will be negative, indicating that the reaction is product-favored at high temperature.
In summary, at high temperatures, the given reaction will be product-favored due to the negative enthalpy change (ΔHr) and the positive entropy change (ΔSr).