Chemistry: Matter and Change
1st Edition
ISBN: 9780078746376
Author: Dinah Zike, Laurel Dingrando, Nicholas Hainen, Cheryl Wistrom
Publisher: Glencoe/McGraw-Hill School Pub Co
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![**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. \( \text{Pb}(s) + \text{Cl}_2(g) \rightarrow \text{PbCl}_2(s) \)
\[ \Delta H^\circ = -359.4 \, \text{kJ} \]
---
**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:
\[ \Delta H^\circ = \boxed{\,\,} \, \text{kJ} \]
---
**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.](https://content.bartleby.com/qna-images/question/4295bf62-da14-49f1-b3bf-6e678bc68de3/a2e35ae7-8859-49a8-8485-b9331f269bd6/cwvp43_processed.jpeg)
Transcribed Image Text:**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. \( \text{Pb}(s) + \text{Cl}_2(g) \rightarrow \text{PbCl}_2(s) \)
\[ \Delta H^\circ = -359.4 \, \text{kJ} \]
---
**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:
\[ \Delta H^\circ = \boxed{\,\,} \, \text{kJ} \]
---
**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.
Transcribed Image Text:**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**
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