Ch.6 - Thermochemistry WorksheetSee all chapters
All Chapters
Ch.1 - Intro to General Chemistry
Ch.2 - Atoms & Elements
Ch.3 - Chemical Reactions
BONUS: Lab Techniques and Procedures
BONUS: Mathematical Operations and Functions
Ch.4 - Chemical Quantities & Aqueous Reactions
Ch.5 - Gases
Ch.6 - Thermochemistry
Ch.7 - Quantum Mechanics
Ch.8 - Periodic Properties of the Elements
Ch.9 - Bonding & Molecular Structure
Ch.10 - Molecular Shapes & Valence Bond Theory
Ch.11 - Liquids, Solids & Intermolecular Forces
Ch.12 - Solutions
Ch.13 - Chemical Kinetics
Ch.14 - Chemical Equilibrium
Ch.15 - Acid and Base Equilibrium
Ch.16 - Aqueous Equilibrium
Ch. 17 - Chemical Thermodynamics
Ch.18 - Electrochemistry
Ch.19 - Nuclear Chemistry
Ch.20 - Organic Chemistry
Ch.22 - Chemistry of the Nonmetals
Ch.23 - Transition Metals and Coordination Compounds
Nature of Energy
Kinetic & Potential Energy
First Law of Thermodynamics
Internal Energy
Endothermic & Exothermic Reactions
Heat Capacity
Constant-Pressure Calorimetry
Constant-Volume Calorimetry
Thermal Equilibrium
Thermochemical Equations
Formation Equations
Enthalpy of Formation
Hess's Law
Additional Guides

Thermochemical Equations involve a balanced chemical equation with a given enthalpy value.

Thermochemical Equations

Concept #1: Thermochemical Equations

Concept #2: Thermochemical Stoichiometric Chart

A modified version of the stoichiometric chart can used for thermochemical equations.

Example #1: Consider the following thermochemical reaction:

How many grams of MgO are produced during an enthalpy change of –375 kJ?

Practice: Nitromethane (CH3NO2), sometimes used as a fuel for drag racing, burns according to the following reaction: 

4 CH3NO2 (l) + 7 O2 (g) → 4 CO2 (g) + 6 H2O (g) + 4 NO2 (g)      ∆Hº = – 2441.6 kJ

How much heat is released by burning 125.0 g of nitromethane (MW: 61.044 g/mol)? 

Practice: Consider the following reaction: 

2 C6H6 (l) + 15 O2 (g) → 12 CO2 (g) + 6 H2­O (g)   ∆Hº = – 6278 kJ

What volume of benzene (C6H6, d = 0.880 g/mL, molar mass = 78.11 g/mol) is necessary to evolve 5.19 x 109 kJ of heat? 

Practice: The creation of liquid methanol is accomplished by the hydrogenation of carbon monoxide: 

CO (g) + 2 H2 (g) → CH3OH (l)       ∆Hº = – 128.1 kJ

How much heat (in kJ) is released when 125.0 g CO reacts with 2.32 x 102 g H2?