- 5.7 Apply Hess Law - using Standard heats of formation, calculate for the the standard Enthalpy Change following reaction. NH4Cl (aq) → NH3 (g) + HCl(aq) KJ Answer:
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.
![**Chapter 5, Section 7**
- **5.7 Apply Hess's Law**
- Using standard heats of formation, calculate the standard enthalpy change for the following reaction:
\[
\text{NH}_4\text{Cl (aq)} \rightarrow \text{NH}_3 \text{ (g) } + \text{HCl (aq)}
\]
**Answer:** ____ kJ
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This section involves applying Hess's Law to determine the standard enthalpy change for a given chemical reaction. Remember, Hess's Law states that the total enthalpy change for a reaction is the same, no matter what pathway is taken, provided the initial and final conditions are the same. Using standard heats of formation from data tables will help in calculating the enthalpy change for the reaction.](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2Fff41355b-6f8b-4225-8cd5-fca5fbd25375%2F5d7daea4-fe3d-4c0b-a813-efac0ce66aba%2Fn8bfqik_processed.jpeg&w=3840&q=75)
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