Skip to main content
Pearson+ LogoPearson+ Logo
Ch.6 - Thermochemistry
All textbooksTro 4th EditionCh.6 - ThermochemistryProblem 84d
Chapter 6, Problem 84d

Write an equation for the formation of each compound from its elements in their standard states, and find ΔH°rxn for each in Appendix IIB. d. CH3OH(l)

Verified step by step guidance
1
Identify the elements that make up CH_3OH(l): carbon (C), hydrogen (H), and oxygen (O).
Determine the standard states of these elements: C is graphite, H is H_2(g), and O is O_2(g).
Write the balanced chemical equation for the formation of CH_3OH(l) from its elements in their standard states: C(graphite) + 2H_2(g) + 1/2O_2(g) -> CH_3OH(l).
Look up the standard enthalpy of formation (ΔH_f°) for CH_3OH(l) in Appendix IIB.
Use the ΔH_f° value from the appendix to find ΔH °_rxn for the formation reaction.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
52s
Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Standard State

The standard state of a substance is its most stable form at 1 bar of pressure and a specified temperature, usually 25°C. For elements, this means their natural state, such as O2(g) for oxygen and C(s) for carbon. Understanding standard states is crucial for writing formation equations, as it ensures that the reactants are in their correct physical states.
Recommended video:
Guided course
01:10
Standard Reduction Potentials

Formation Reaction

A formation reaction is a chemical reaction in which one mole of a compound is formed from its constituent elements in their standard states. The equation for such a reaction typically includes the elements on the reactant side and the compound on the product side. For example, the formation of methanol (CH3OH) from carbon, hydrogen, and oxygen would involve writing the balanced equation that reflects this process.
Recommended video:
Guided course
02:34
Enthalpy of Formation

Enthalpy Change (ΔH°rxn)

The enthalpy change (ΔH°rxn) for a reaction at standard conditions represents the heat absorbed or released during the reaction. It is a key thermodynamic quantity that can be found in tables or calculated using Hess's law. For the formation of CH3OH(l), ΔH°rxn indicates whether the reaction is exothermic or endothermic, providing insight into the stability of the compound relative to its elements.
Recommended video:
Guided course
02:34
Enthalpy of Formation
Related Practice
Textbook Question

Write an equation for the formation of each compound from its elements in their standard states, and find ΔH°rxn for each in Appendix IIB. a. NO2(g)

Textbook Question

Write an equation for the formation of each compound from its elements in their standard states, and find ΔH°rxn for each in Appendix IIB. b. MgCO3(s)

Textbook Question

Hydrazine (N2H4) is a fuel used by some spacecraft. It is normally oxidized by N2O4 according to the equation: N2H4 (l) + N2O4 (g) → 2 N2O (g) + 2 H2O (g) Calculate ΔH°rxn for this reaction using standard enthalpies of formation.

Textbook Question

Pentane (C5H12) is a component of gasoline that burns according to the following balanced equation: C5H12(l) + 8 O2(g) → 5 CO2(g) + 6 H2O(g) Calculate ΔH°rxn for this reaction using standard enthalpies of formation. (The standard enthalpy of formation of liquid pentane is –146.8 kJ/mol.)

1
views