Textbook Question
Given the data N2(g) + O2(g) → 2 NO(g) ΔH = +180.7 kJ 2 NO(g) + O2(g) → 2 NO2(g) ΔH = -113.1 kJ 2 N2O(g) → 2 N2(g) + O2(g) ΔH = -163.2 kJ use Hess's law to calculate ΔH for the reaction N2O(g) + NO2(g) → 3 NO(g)
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Ch.5 - Thermochemistry
Brown15th EditionChemistry: The Central ScienceISBN: 9780137542970
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Table of contents
- Ch.1 - Introduction: Matter, Energy, and Measurement111
- Ch.2 - Atoms, Molecules, and Ions166
- Ch.3 - Chemical Reactions and Reaction Stoichiometry138
- Ch.4 - Reactions in Aqueous Solution127
- Ch.5 - Thermochemistry104
- Ch.6 - Electronic Structure of Atoms109
- Ch.7 - Periodic Properties of the Elements107
- Ch.8 - Basic Concepts of Chemical Bonding102
- Ch.9 - Molecular Geometry and Bonding Theories120
- Ch.10 - Gases122
- Ch.11 - Liquids and Intermolecular Forces79
- Ch.12 - Solids and Modern Materials102
- Ch.13 - Properties of Solutions99
- Ch.14 - Chemical Kinetics153
- Ch.15 - Chemical Equilibrium83
- Ch.16 - Acid-Base Equilibria109
- Ch.17 - Additional Aspects of Aqueous Equilibria117
- Ch.18 - Chemistry of the Environment60
- Ch.19 - Chemical Thermodynamics109
- Ch.20 - Electrochemistry113
- Ch.21 - Nuclear Chemistry79
- Ch.22 - Chemistry of the Nonmetals52
- Ch.23 - Transition Metals and Coordination Chemistry57
- Ch.24 - The Chemistry of Life: Organic and Biological Chemistry7
Brown15th EditionChemistry: The Central ScienceISBN: 9780137542970Not the one you use?Change textbook
Chapter 5, Problem 72a
Write balanced equations that describe the formation of the following compounds from elements in their standard states, and then look up the standard enthalpy of formation for each substance in Appendix C: (a) NH4NO3(s)
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Identify the elements in their standard states that are needed to form NH_4NO_3(s). These are nitrogen (N_2), hydrogen (H_2), and oxygen (O_2).
Write the balanced chemical equation for the formation of NH_4NO_3(s) from its elements: \[ \frac{1}{2}N_2(g) + \frac{3}{2}H_2(g) + \frac{3}{2}O_2(g) \rightarrow NH_4NO_3(s) \]
Ensure that the equation is balanced in terms of both atoms and charge. In this case, the equation is balanced as written.
Look up the standard enthalpy of formation (\( \Delta H_f^\circ \)) for NH_4NO_3(s) in Appendix C or a reliable chemistry data source.
The standard enthalpy of formation is the change in enthalpy when one mole of a compound is formed from its elements in their standard states under standard conditions (298 K and 1 atm).
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Balanced Chemical Equations
A balanced chemical equation represents a chemical reaction where the number of atoms for each element is the same on both sides of the equation. This is crucial for obeying the law of conservation of mass, which states that matter cannot be created or destroyed in a chemical reaction. Balancing equations involves adjusting coefficients to ensure that the total number of each type of atom is equal, reflecting the actual stoichiometry of the reaction.
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Balancing Chemical Equations
Standard States of Elements
The standard state of an element refers to its most stable form at a specified temperature (usually 25°C) and pressure (1 atm). For example, the standard state of nitrogen is N2 gas, while that of carbon is graphite. Understanding standard states is essential for accurately writing formation reactions, as the enthalpy of formation is calculated based on elements in their standard states.
Standard Enthalpy of Formation
The standard enthalpy of formation (ΔHf°) is the change in enthalpy when one mole of a compound is formed from its elements in their standard states. This value is crucial for thermodynamic calculations and helps predict the energy changes associated with chemical reactions. It is typically found in tables and is used to calculate the overall enthalpy change for reactions involving the formation of compounds.
Related Practice
Textbook Question
Using values from Appendix C, calculate the value of H for each of the following reactions: (a) NiO(s) + 2 HCl(g) → NiCl2(s) + H2O(g)
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Textbook Question
For each of the following compounds, write a balanced thermochemical equation depicting the formation of one mole of the compound from its elements in their standard states and then look up H °f for each substance in Appendix C. (b) FeCl3(s)
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Textbook Question
The concentration of alcohol 1CH3CH2OH2 in blood, called the 'blood alcohol concentration' or BAC, is given in units of grams of alcohol per 100 mL of blood. The legal definition of intoxication, in many states of the United States, is that the BAC is 0.08 or higher. What is the concentration of alcohol, in terms of molarity, in blood if the BAC is 0.08?
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Textbook Question
Complete combustion of 1 mol of acetone (C3H6O) liberates 1790 kJ: C3H6O(l) + 4 O2(g) → 3 CO2(g) + 3 H2O(l) ΔH° = -1790 kJ Using this information together with the standard enthalpies of formation of O2(g), CO2(g), and H2O(l) from Appendix C, calculate the standard enthalpy of formation of acetone.
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