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

Solution: The United States gets 95% of its hydrogen gas by "steam reforming" methane, CH4(g). Another option is the “partial oxidation” of hydrocarbons to make carbon monoxide and hydrogen gas. For octane, th

Problem

The United States gets 95% of its hydrogen gas by "steam reforming" methane, CH4(g).

Another option is the “partial oxidation” of hydrocarbons to make carbon monoxide and hydrogen gas. For octane, that reaction would be 

C8H18(l) + 4O2(g) → 8CO(g) + 9H2(g) 

 We know ΔH° for the combustion of octane 

C8H18(l) + 25/2 O2(g) → 8CO2(g) + 9H2O(l)      ΔH° = -5500 kJ/mol 

Assume the arbitrary values below for the combustion reactions of carbon monoxide and hydrogen:

CO(g) + 1/2 O2(g) → CO2(g)             ΔH° = “-290 kJ/mol” 

H2(g) + 1 /2O2(g) → H2O(l)               ΔH° = “-285 kJ/mol”

A. Do you expect the magnitude of ΔH° for the partial oxidation of octane, to be greater or less than the magnitude of ΔH° for the combustion of octane? Explain.

 

 

B. Now, determine   ΔH°  for the partial oxidation of octane with those assigned values. Choose from the choices below

 

 

 

 

C. Do you think the hydrogen produced provides more or less energy than you would get from the combustion of octane? Explain.