Textbook Question
Calculate ∆H°f in kJ/mol for benzene, C6H6, from the following data: 2 C6H6(l) + 15 O2(g) → 12 CO2(g) + 6 H2O(l) ∆H°=-6534 kJ ∆H°f (CO2) = -393.5 kJ/mol ∆H°f(H2O) = -285.8 kJ/mol
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Ch.9 - Thermochemistry: Chemical Energy
McMurry8th EditionChemistryISBN: 9781292336145
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Table of contents
- Ch.1 - Chemical Tools: Experimentation & Measurement170
- Ch.2 - Atoms, Molecules & Ions160
- Ch.3 - Mass Relationships in Chemical Reactions169
- Ch.4 - Reactions in Aqueous Solution199
- Ch.5 - Periodicity & Electronic Structure of Atoms102
- Ch.6 - Ionic Compounds: Periodic Trends and Bonding Theory92
- Ch.7 - Covalent Bonding and Electron-Dot Structures61
- Ch.8 - Covalent Compounds: Bonding Theories and Molecular Structure59
- Ch.9 - Thermochemistry: Chemical Energy122
- Ch.10 - Gases: Their Properties & Behavior155
- Ch.11 - Liquids & Phase Changes54
- Ch.12 - Solids and Solid-State Materials73
- Ch.13 - Solutions & Their Properties120
- Ch.14 - Chemical Kinetics98
- Ch.15 - Chemical Equilibrium125
- Ch.16 - Aqueous Equilibria: Acids & Bases110
- Ch.17 - Applications of Aqueous Equilibria147
- Ch.18 - Thermodynamics: Entropy, Free Energy & Equilibrium86
- Ch.19 - Electrochemistry154
- Ch.20 - Nuclear Chemistry96
- Ch.21 - Transition Elements and Coordination Chemistry156
- Ch.22 - The Main Group Elements187
- Ch.23 - Organic and Biological Chemistry51
Chapter 9, Problem 103c
Write balanced equations for the formation of the following compounds from their elements. (c) Dichloromethane (a liquid, CH2Cl2)
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Identify the elements involved in the formation of dichloromethane, which are carbon (C), hydrogen (H), and chlorine (Cl).
Write the unbalanced equation using the molecular formula of dichloromethane (CH2Cl2) and the elemental forms of carbon, hydrogen, and chlorine. The elemental form of carbon is solid carbon (C), hydrogen is dihydrogen (H2), and chlorine is dichlorine (Cl2). The unbalanced equation is: C(s) + H2(g) + Cl2(g) → CH2Cl2(l).
Balance the carbon atoms first. Since there is one carbon atom in CH2Cl2 and one in elemental carbon, the carbon atoms are already balanced.
Next, balance the hydrogen atoms. There are two hydrogen atoms in CH2Cl2 and two in one molecule of dihydrogen (H2), so the hydrogen atoms are balanced with one molecule of H2.
Finally, balance the chlorine atoms. There are two chlorine atoms in CH2Cl2 and two in one molecule of dichlorine (Cl2), so the chlorine atoms are balanced with one molecule of Cl2. The balanced chemical equation is: C(s) + H2(g) + Cl2(g) → CH2Cl2(l).
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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 involves adjusting coefficients in front of compounds to ensure that the total number of each type of atom is equal.
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Balancing Chemical Equations
Formation Reactions
A formation reaction is a specific type of chemical reaction where a compound is formed from its constituent elements in their standard states. For example, when forming dichloromethane (CH2Cl2), chlorine gas (Cl2) and carbon (C) in its solid form, along with hydrogen gas (H2), are combined. Understanding formation reactions is essential for writing accurate equations for compound synthesis.
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Standard States of Elements
The standard state of an element refers to its physical state and form at a specified temperature and pressure, typically 25°C and 1 atm. For example, carbon is solid (graphite), hydrogen is a gas (H2), and chlorine is also a gas (Cl2) at these conditions. Recognizing the standard states of elements is vital for correctly writing formation reactions and ensuring that the reactants are represented accurately.
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Related Practice
Textbook Question
Write balanced equations for the formation of the following compounds from their elements. (b) Sodium sulfate
Textbook Question
Write balanced equations for the formation of the following compounds from their elements. (b) Sucrose (table sugar, C12H22O11)
Textbook Question
Sulfuric acid (H2SO4), the most widely produced chemical in the world, is amde yb a two-step oxidaiton of sulfur to sulfur trioxide, SO3, followed by reaciton with water. Calculate ΔH°f for SO3 in kJ/mol, given the following data: S(s) + O2(g) → SO2(g) ΔH° = -296.8 kJ SO2(g) + 1/2 O2(g) → SO3(g) ΔH° = -98.9 kJ
Textbook Question
Write balanced equations for the formation of the following compounds from their elements. (a) Ethanol (C2H6O)
Textbook Question
The standard enthalpy change for the reaciton of SO3(g) with H2O(l) to yield H2SO4(aq) is ΔH° = -227.8 kJ. Use the information in Problem 9.104 to calculate ΔH°f for H2SO4(aq) in kJ/mol. [For H2O(l), ΔH°f = -285.88 kJ/mol.]
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