Given the standard enthalpy changes for the following two reactions: ΔΗ° – 434.6 kJ (1) 2Pb(s) + O2(g) → 2PbO(s) (2) Pb(s) + Cl2(g) → PbCl2(s) -- – 359.4 kJ ΔΗ° what is the standard enthalpy change for the reaction: (3) 2PbCl2(s) + O2(g) → 2PbO(s) + 2Cl2(g) ΔΗ° =? = ΔΗ° 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.
![**Understanding Standard Enthalpy Changes**
Given the standard enthalpy changes for the following two reactions:
1. \( \text{2Pb}(s) + \text{O}_2(g) \rightarrow \text{2PbO}(s) \)
\[ \Delta H^\circ = -434.6 \, \text{kJ} \]
2. \( \text{Pb}(s) + \text{Cl}_2(g) \rightarrow \text{PbCl}_2(s) \)
\[ \Delta H^\circ = -359.4 \, \text{kJ} \]
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**Goal:**
Determine the standard enthalpy change for the following reaction:
3. \( \text{2PbCl}_2(s) + \text{O}_2(g) \rightarrow \text{2PbO}(s) + \text{2Cl}_2(g) \)
\[ \Delta H^\circ = \, \text{?} \]
Fill in the box with the calculated standard enthalpy change:
\[ \Delta H^\circ = \boxed{\,\,} \, \text{kJ} \]
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**Explanation for Educators:**
This problem involves calculating the standard enthalpy change for a reaction using known values from related reactions. It applies principles from Hess’s Law, which states that if a reaction is the sum of two or more other reactions, the total enthalpy change is the sum of the enthalpy changes for the individual reactions. Students are tasked with rearranging and manipulating given reactions to derive the enthalpy change of the target reaction, highlighting skills in thermochemistry and stoichiometry.](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F4295bf62-da14-49f1-b3bf-6e678bc68de3%2Fa2e35ae7-8859-49a8-8485-b9331f269bd6%2Fcwvp43_processed.jpeg&w=3840&q=75)
![**Enthalpy Change in Chemical Reactions**
**Given the standard enthalpy changes for the following two reactions:**
1. \(2\text{C}(s) + 2\text{H}_2(g) \rightarrow \text{C}_2\text{H}_4(g)\) \(\Delta H^\circ = 52.3\, \text{kJ}\)
2. \(2\text{C}(s) + 3\text{H}_2(g) \rightarrow \text{C}_2\text{H}_6(g)\) \(\Delta H^\circ = -84.7\, \text{kJ}\)
**What is the standard enthalpy change for the following reaction?**
3. \(\text{C}_2\text{H}_4(g) + \text{H}_2(g) \rightarrow \text{C}_2\text{H}_6(g)\) \(\Delta H^\circ =?\)
**Standard enthalpy change = \_\_\_ kJ**](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F4295bf62-da14-49f1-b3bf-6e678bc68de3%2Fa2e35ae7-8859-49a8-8485-b9331f269bd6%2F4qtub9s_processed.jpeg&w=3840&q=75)
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