When a concentrated NaCl aqueous solution is electrolyzed, what is the reason for the stabality of the products to be lesser stable as of thermodynamically, with respect to the reactants?
Is it because the products are gasses?
H20(l) +4e--->H2(g) + 2OH-(aq)
2 Cl-(aq)--->Cl2(g) + 2e
Or is the change of the value of enthalpy for this reaction is positive.(we are thought that USUALLY(not in all cases) ,if the change in enthalpy ∆H is positive the products are not very stable)
The stability of the products in an electrolysis reaction is determined by both the nature of the products and the thermodynamic factors involved. In the case of electrolysis of a concentrated NaCl solution:
1. Nature of the products: One of the products of electrolysis is chlorine gas (Cl2) which is indeed a gas. Gas molecules tend to be less stable compared to liquid or solid molecules because they are more easily dispersed and have higher molecular mobility. This is partly why gases are generally less stable compared to other phases.
2. Thermodynamic factors: The thermodynamic stability of the products can also be evaluated by considering the change in enthalpy (∆H) of the reaction. A positive value of ∆H generally indicates an endothermic reaction, meaning the energy required to break the bonds is greater than the energy released in forming the new bonds. This suggests that the products are not as thermodynamically stable as the reactants, where a negative ∆H value indicates an exothermic reaction and greater thermodynamic stability.
In the case of the electrolysis of a concentrated NaCl solution, the ∆H value for the overall reaction is positive because the energy needed to break the bonds in water (H2O) and chloride ions (Cl-) is greater than the energy released in forming hydrogen gas (H2) and hydroxide ions (OH-). This, in turn, contributes to the lower stability of the products compared to the reactants in the reaction.
So, it is both the nature of the products, particularly the formation of a gas, and the positive change in enthalpy (∆H) that contribute to the lesser stability of the products in this electrolysis reaction.