(7.6) Aluminum oxide decomposes to aluminum and oxygen gas by the following reaction. Al2O3(s) 2Al(s) + 3/2 O2(g) → A Hrxn = 1676 kJ Is this reaction endothermic or exothermic? [Choose ] [Choose ] 1676 kJ If 1.049 moles of aluminum was formed by the reaction, how much heat (kJ) would be involved? 440 kJ endothermic 1760 kJ 879 kJ exothermic
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.
![### Thermodynamics of Aluminum Oxide Decomposition
**Reaction Equation:**
\[ \text{Al}_2\text{O}_3 (s) \rightarrow 2 \text{Al} (s) + \frac{3}{2} \text{O}_2 (g) \]
\[ \Delta H_{\text{rxn}} = 1676 \text{ kJ} \]
#### Question 1:
**Is this reaction endothermic or exothermic?**
- [Choose]
- 1676 kJ
- 440 kJ
- endothermic
- 1760 kJ
- 879 kJ
- exothermic
#### Question 2:
**If 1.049 moles of aluminum were formed by the reaction, how much heat (kJ) would be involved?**
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**Explanation:**
The provided image contains a chemical reaction where aluminum oxide (\(\text{Al}_2\text{O}_3\)) decomposes into aluminum (\(\text{Al}\)) and oxygen gas (\(\(\text{O}_2)\)). The reaction has an enthalpy change \(\(\Delta H_{\text{rxn}}\)) of 1676 kJ. The nature of the reaction, whether it is endothermic or exothermic, needs to be determined by identifying whether heat is absorbed or released. Additionally, if a specific amount of aluminum is formed, the heat involved in the reaction can be calculated.
- **Endothermic Reaction:** Absorbs heat from the surroundings (\(\Delta H > 0\)).
- **Exothermic Reaction:** Releases heat to the surroundings (\(\Delta H < 0\)).
Given that \(\(\Delta H_{\text{rxn}}\)) is a positive value (1676 kJ), this reaction is endothermic, meaning it absorbs heat.
For calculating the heat involved when 1.049 moles of aluminum are formed:
- According to the stoichiometric equation, 2 moles of aluminum require 1676 kJ of heat.
- For 1.049 moles of aluminum:
\[ \text{Heat involved} = \frac{1676 \text{ kJ} }{2} \times 1.049 = 440 \text{ kJ} \]
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