Use the molar bond enthalpy data in the table to estimate Average molar bond enthalpies. (Hbond) the value of AHan for the equation Bond kJ - mol- Bond kJ - mol- NH, (g) + 20, (g) HNO,(g) + H, O(g) > O-H 464 C=N 890 The bonding in the molecules is shown. 0-0 142 N-H 390 C-0 351 N-O 201 -> O=0 502 N=N 418 C=0 730 N=O 607 С-С 347 F-F 155 С-С 615 Cl-CI 243 C=C 811 Br-Br 192 С-Н 414 Н-Н 435 C-F 439 Н-F 565 C-CI 331 H-CI 431 С-Br 276 Н-Br 368 C-N 293 H-S 364 C=N 615 S-S 225 AHan = kJ
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.
![**General Chemistry 4th Edition**
*McQuarrie • Rock • Gallogly*
**University Science Books**
presented by Macmillan Learning
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### Exercise: Estimating ΔH_rxn Using Molar Bond Enthalpy Data
Use the molar bond enthalpy data in the table to estimate the value of ΔH_rxn for the following equation:
\[ \text{NH}_3(g) + 2\text{O}_2(g) \rightarrow \text{HNO}_3(g) + \text{H}_2\text{O}(g) \]
**The bonding in the molecules is shown:**
(Refer to molecular structures shown in the image)
### Average Molar Bond Enthalpies (\( H_{\text{bond}} \))
| Bond | kJ·mol\(^{-1}\) | Bond | kJ·mol\(^{-1}\) |
|-------|-----------------|-------|-----------------|
| O–H | 464 | C≡N | 890 |
| O–O | 142 | N–H | 390 |
| C–O | 351 | N=O | 201 |
| O=O | 502 | N–O | 418 |
| C=O | 730 | N=O | 607 |
| C–C | 347 | F–F | 155 |
| C=C | 615 | Cl–Cl | 243 |
| C≡C | 811 | Br–Br | 192 |
| C–H | 414 | H–I | 299 |
| C–N | 305 | H–Br | 365 |
| C–F | 439 | H–Cl | 431 |
| C–Br | 276 | H–S | 364 |
| C=N | 615 | S–S | 225 |
\[ \Delta H_{\text{rxn}} = \]
\[ \boxed{\text{(Fill in the value)}} \text{ kJ} \]
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Use the above data to estimate bond enthalpies in a chemical reaction. Calculation involves determining the](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F6dbc0877-d53f-4c9c-9eec-5fc7749c806c%2F10187086-4ee9-400f-af5e-96d728e78bdc%2Fx9280x6_processed.jpeg&w=3840&q=75)
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