Thermochemistry
Thermochemistry can be considered as a branch of thermodynamics that deals with the connections between warmth, work, and various types of energy, formed because of different synthetic and actual cycles. Thermochemistry describes the energy changes that occur as a result of reactions or chemical changes in a substance.
Exergonic Reaction
The term exergonic is derived from the Greek word in which ‘ergon’ means work and exergonic means ‘work outside’. Exergonic reactions releases work energy. Exergonic reactions are different from exothermic reactions, the one that releases only heat energy during the course of the reaction. So, exothermic reaction is one type of exergonic reaction. Exergonic reaction releases work energy in different forms like heat, light or sound. For example, a glow stick releases light making that an exergonic reaction and not an exothermic reaction since no heat is released. Even endothermic reactions at very high temperature are exergonic.
Consider the following reaction. Balance the reaction and use bond energies to estimate ΔHorxn Is the reaction exothermic or endothermic
![**Chemical Reaction: Methane and Chlorine Gas**
**Reaction:**
\[ \text{CH}_4(g) + \text{Cl}_2(g) \rightarrow \text{CHCl}_3 + \text{HCl} \]
**Description:**
In this reaction, methane (\(\text{CH}_4\)) reacts with chlorine gas (\(\text{Cl}_2\)) to produce chloroform (\(\text{CHCl}_3\)) and hydrogen chloride (\(\text{HCl}\)).
**Diagram Explanation:**
- **Reactants:**
- Methane (\(\text{CH}_4\)): A single carbon atom bonded to four hydrogen atoms in a tetrahedral structure.
- Chlorine (\(\text{Cl}_2\)): Represented as diatomic chlorine gas.
- **Products:**
- Chloroform (\(\text{CHCl}_3\)): A carbon atom bonded to one hydrogen and three chlorine atoms, depicted with chlorine atoms surrounding the carbon.
- Hydrogen chloride (\(\text{HCl}\)): Formed as a byproduct, consisting of a single hydrogen atom bonded to a chlorine atom.
**Note:**
All products are in gaseous form.](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2Fd4a05f9c-c7ed-455e-9c75-f4b90c76fcea%2F632caab9-5c3d-412b-baf0-e725200bcc27%2Fthmc7i6_processed.png&w=3840&q=75)
The type of reaction whether the reaction is endothermic or exothermic can be determined through the enthalpy of reaction. The enthalpy of reaction can be determined by calculating the energy spent during the breaking of bond and energy released during the formation of the bond. If the overall enthalpy is negative then the given reaction would be exothermic otherwise if the enthalpy is positive then the reaction would be endothermic. Bond energy is the average energy required breaking the bond; it also gives bond strength.
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