Chemistry
10th Edition
ISBN:9781305957404
Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Chapter1: Chemical Foundations
Section: Chapter Questions
Problem 1RQ: Define and explain the differences between the following terms. a. law and theory b. theory and...
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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.
Question
Use the table below or above to solve. TYSM :) Keep in mind sig figs plz.
![**Calculating Enthalpy Change using Provided Data**
**Problem:**
Using the table provided, what is the enthalpy for the reaction shown below:
\[ 2NO_2 (g) \rightarrow N_2 (g) + 2O_2 (g) \]
**Solution:**
To determine the enthalpy change (\(\Delta H\)) for this reaction, you typically need to use the standard enthalpies of formation (\(\Delta H_f^\circ\)) of the reactants and products, often found in the provided table. The standard enthalpy change of the reaction can be calculated using the formula:
\[ \Delta H^\circ_{reaction} = \sum \Delta H_f^\circ \text{(products)} - \sum \Delta H_f^\circ \text{(reactants)} \]
Follow these steps:
1. Write the balanced chemical equation.
2. Identify the reactants and products along with their respective standard enthalpies of formation (\(\Delta H_f^\circ\)) from the table.
3. Calculate the sum of the enthalpy values for the products, each multiplied by its coefficient in the balanced equation.
4. Calculate the sum of the enthalpy values for the reactants, each multiplied by its coefficient in the balanced equation.
5. Subtract the sum for the reactants from the sum for the products to obtain the standard enthalpy change of the reaction.
**Example Calculation (Assume hypothetical values for illustration):**
- Standard enthalpy of formation for \(NO_2 (g)\): \(\Delta H_f^\circ = x\) kJ/mol
- Standard enthalpy of formation for \(N_2 (g)\): \(\Delta H_f^\circ = y\) kJ/mol
- Standard enthalpy of formation for \(O_2 (g)\): \(\Delta H_f^\circ = z\) kJ/mol
Using the formula:
\[ \Delta H^\circ_{reaction} = [ \Delta H_f^\circ (N_2) + 2 \Delta H_f^\circ (O_2)] - [2 \Delta H_f^\circ (NO_2)] \]
\[ \Delta H^\circ_{reaction} = [y + 2z] - [2x] \]
Given specific values for \(x\), \(y\), and \(z\) from the](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F2dc05801-0f2f-4b82-9bd0-eb38a3fb827a%2F13f0c067-3290-40f8-93f7-013ca1f36616%2F6p6zxl9_processed.png&w=3840&q=75)
Transcribed Image Text:**Calculating Enthalpy Change using Provided Data**
**Problem:**
Using the table provided, what is the enthalpy for the reaction shown below:
\[ 2NO_2 (g) \rightarrow N_2 (g) + 2O_2 (g) \]
**Solution:**
To determine the enthalpy change (\(\Delta H\)) for this reaction, you typically need to use the standard enthalpies of formation (\(\Delta H_f^\circ\)) of the reactants and products, often found in the provided table. The standard enthalpy change of the reaction can be calculated using the formula:
\[ \Delta H^\circ_{reaction} = \sum \Delta H_f^\circ \text{(products)} - \sum \Delta H_f^\circ \text{(reactants)} \]
Follow these steps:
1. Write the balanced chemical equation.
2. Identify the reactants and products along with their respective standard enthalpies of formation (\(\Delta H_f^\circ\)) from the table.
3. Calculate the sum of the enthalpy values for the products, each multiplied by its coefficient in the balanced equation.
4. Calculate the sum of the enthalpy values for the reactants, each multiplied by its coefficient in the balanced equation.
5. Subtract the sum for the reactants from the sum for the products to obtain the standard enthalpy change of the reaction.
**Example Calculation (Assume hypothetical values for illustration):**
- Standard enthalpy of formation for \(NO_2 (g)\): \(\Delta H_f^\circ = x\) kJ/mol
- Standard enthalpy of formation for \(N_2 (g)\): \(\Delta H_f^\circ = y\) kJ/mol
- Standard enthalpy of formation for \(O_2 (g)\): \(\Delta H_f^\circ = z\) kJ/mol
Using the formula:
\[ \Delta H^\circ_{reaction} = [ \Delta H_f^\circ (N_2) + 2 \Delta H_f^\circ (O_2)] - [2 \Delta H_f^\circ (NO_2)] \]
\[ \Delta H^\circ_{reaction} = [y + 2z] - [2x] \]
Given specific values for \(x\), \(y\), and \(z\) from the
Transcribed Image Text:### Enthalpy of Various Chemical Reactions
Below is a table listing different chemical reactions along with their associated enthalpy changes in kilojoules per mole (kJ/mol). The enthalpy change indicates whether the reaction is exothermic (negative values) or endothermic (positive values).
| **Reaction** | **Enthalpy (kJ/mol)** |
|--------------------------------------|-----------------------|
| CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(l) | -890.4 |
| C₃H₈(g) + 5O₂(g) → 3CO₂(g) + 2H₂O(l) | -2219.2 |
| C₆H₁₂O₆(s) + 6O₂(g) → 6CO₂(g) + 6H₂O(l) | -2804 |
| C(s) + O₂(g) → CO₂(g) | -393.5 |
| 2CO(g) + O₂(g) → 2CO₂(g) | -566.0 |
| 2H₂(g) + O₂(g) → 2H₂O(g) | -483.6 |
| 2H₂(g) + O₂(g) → 2H₂O(l) | -571.6 |
| N₂(g) + 2O₂(g) → 2NO₂(g) | 66.4 |
| N₂(g) + O₂(g) → 2NO(g) | 182.6 |
| N₂(g) + 3H₂(g) → 2NH₃(g) | -91.8 |
| H₂(g) + I₂(g) → 2HI(g) | 53.0 |
#### Explanation:
- **Exothermic Reactions**: These reactions release energy, indicated by negative enthalpy values. For example, the combustion of methane (CH₄) with oxygen (O₂) to produce carbon dioxide (CO₂) and water (H₂O) releases -890.4 kJ/mol.
- **Endothermic Reactions**: These reactions absorb energy, indicated by positive enthalpy values. For instance,
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