Hi, it would be great if I could have some help with the following questions :)
1. Given the reasoning that the standard enthalpy change of neutralisation between weak acids/bases and strong acids/bases is lower as compared to those between strong acids and bases because energy is absorbed to ionize the undissociated weak acid/base, why is the standard enthalpy change of the reaction:
CH3COOH + NH3 -> H2O + CH3COONH4
greater than that of neutralisation between weak acids/bases and strong acids/bases since there should be more energy absorbed to ionize the greater number of undissociated acid/base?
2. Since the units of enthalpy change of reaction is kJ/mol, why does changing the stochiometry coefficients still change the enthalpy change of a reaction? Should this not be analogous to the concept of heat capacity and specific heat capacity, where the value of the specific heat capacity is constant for a particular material, regardless of mass, since the units of specific heat capacity already “accounts” for the mass?
Originally posted by Cre8ion:Hi, it would be great if I could have some help with the following questions :)
1. Given the reasoning that the standard enthalpy change of neutralisation between weak acids/bases and strong acids/bases is lower as compared to those between strong acids and bases because energy is absorbed to ionize the undissociated weak acid/base, why is the standard enthalpy change of the reaction:
CH3COOH + NH3 -> H2O + CH3COONH4
greater than that of neutralisation between weak acids/bases and strong acids/bases since there should be more energy absorbed to ionize the greater number of undissociated acid/base?
2. Since the units of enthalpy change of reaction is kJ/mol, why does changing the stochiometry coefficients still change the enthalpy change of a reaction? Should this not be analogous to the concept of heat capacity and specific heat capacity, where the value of the specific heat capacity is constant for a particular material, regardless of mass, since the units of specific heat capacity already “accounts” for the mass?
Q1. There is a fundamental misconception with your question (where did you even get this question? Did your JC ask you that? Which JC do you come from?). Neutralization enthalpy is defined as per mole of water generated. No water is generated in the reaction between weak acids and weak bases.
Q2. kJ/mol is not per mole of any particular reactant or product, but per mole of the equation.