Question
Discuss standard enthalpy change of neutralisation with mathematical expression
Answers
GPT-4o mini
The standard enthalpy change of neutralization (\( \Delta H_{\text{neut}}^\circ \)) refers to the enthalpy change that occurs when one mole of water is formed from the reaction between an acid and a base under standard conditions (typically at a temperature of 298 K and a pressure of 1 atm). Neutralization reactions generally involve the reaction of hydrogen ions (\( \text{H}^+ \)) from the acid and hydroxide ions (\( \text{OH}^- \)) from the base to form water (\( \text{H}_2\text{O} \)).
### Mathematical Expression
The standard enthalpy change of neutralization can be expressed with the following equation:
\[
\Delta H_{\text{neut}}^\circ = \frac{\Delta H_{\text{rxn}}}{\text{n}}
\]
where:
- \( \Delta H_{\text{rxn}} \) is the total enthalpy change observed during the neutralization reaction.
- \( n \) is the number of moles of water produced in the reaction.
For a typical strong acid and strong base neutralization, such as hydrochloric acid (\( \text{HCl} \)) reacting with sodium hydroxide (\( \text{NaOH} \)), the balanced chemical equation is:
\[
\text{HCl}(aq) + \text{NaOH}(aq) \rightarrow \text{NaCl}(aq) + \text{H}_2\text{O}(l)
\]
In this case, one mole of water is produced, and thus the standard enthalpy change of neutralization can be expressed as:
\[
\Delta H_{\text{neut}}^\circ = \Delta H_{\text{rxn}}
\]
### Values of Enthalpy Changes
- The standard enthalpy change of neutralization for strong acids with strong bases is typically around \(-57.1 \, \text{kJ/mol}\) which signifies that the reaction is exothermic, meaning it releases heat.
### Summary
In summary, the standard enthalpy change of neutralization quantifies the heat released when an acid neutralizes a base to form water. It is a key concept in thermochemistry and helps to understand the energetic aspects of acid-base reactions.
### Mathematical Expression
The standard enthalpy change of neutralization can be expressed with the following equation:
\[
\Delta H_{\text{neut}}^\circ = \frac{\Delta H_{\text{rxn}}}{\text{n}}
\]
where:
- \( \Delta H_{\text{rxn}} \) is the total enthalpy change observed during the neutralization reaction.
- \( n \) is the number of moles of water produced in the reaction.
For a typical strong acid and strong base neutralization, such as hydrochloric acid (\( \text{HCl} \)) reacting with sodium hydroxide (\( \text{NaOH} \)), the balanced chemical equation is:
\[
\text{HCl}(aq) + \text{NaOH}(aq) \rightarrow \text{NaCl}(aq) + \text{H}_2\text{O}(l)
\]
In this case, one mole of water is produced, and thus the standard enthalpy change of neutralization can be expressed as:
\[
\Delta H_{\text{neut}}^\circ = \Delta H_{\text{rxn}}
\]
### Values of Enthalpy Changes
- The standard enthalpy change of neutralization for strong acids with strong bases is typically around \(-57.1 \, \text{kJ/mol}\) which signifies that the reaction is exothermic, meaning it releases heat.
### Summary
In summary, the standard enthalpy change of neutralization quantifies the heat released when an acid neutralizes a base to form water. It is a key concept in thermochemistry and helps to understand the energetic aspects of acid-base reactions.