Use bond energies to determine AHn for the reaction between ethanol and hydrogen chloride. CH3 CH2OH(9) +HCl(g) → CH3 CH2C1(g) + H2O(g) Average Bond Energies Bond Bond Energy (kJ/mol) Н-С 414 H-0 464 H-F 565 Н-СІ 431 Н-Вг 364 C-C1 339 C-0 360 Cl-F 253 Cl-Cl 243 Br-Cl 218 O -12 kJ O 1549 kJ O -1549 kJ 12 kI
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.
![**Determining ΔH_rxn for the Reaction Between Ethanol and Hydrogen Chloride**
The reaction considered is:
\[ \text{CH}_3\text{CH}_2\text{OH}(g) + \text{HCl}(g) \rightarrow \text{CH}_3\text{CH}_2\text{Cl}(g) + \text{H}_2\text{O}(g) \]
**Table of Average Bond Energies**
| **Bond** | **Bond Energy (kJ/mol)** |
|----------|--------------------------|
| H—C | 414 |
| H—O | 464 |
| H—F | 565 |
| H—Cl | 431 |
| H—Br | 364 |
| C—Cl | 339 |
| C—O | 360 |
| Cl—F | 253 |
| Cl—Cl | 243 |
| Br—Cl | 218 |
Using these bond energies, the enthalpy change for the reaction, \(ΔH_{\text{rxn}}\), can be calculated by summing the energies of the bonds broken and subtracting the sum of the energies of the bonds formed.
Available answer choices include:
- -12 kJ
- 1549 kJ
- -1549 kJ
- 12 kJ
To determine which one is correct, students can follow the steps of breaking down the bonds in the reactants and forming the bonds in the products, and then calculating the total energy change to identify \(ΔH_{\text{rxn}}\).](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2Fbc7df924-6a52-4175-b6ea-9e20e03510e5%2Fda7aae4f-5b3f-4881-aabc-5513d390f3c0%2Fl3qeq4s_processed.png&w=3840&q=75)
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