Lecture

Enthalpy Standard and Hess Law

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Description

This lecture covers the concept of standard enthalpy of formation (Af H) and the application of Hess's Law in determining standard enthalpies. It explains how Af H is related to the formation of a pure substance at standard conditions and how Hess's Law can be used to calculate enthalpies for reactions. Various standard enthalpies, such as fusion, vaporization, ionization, attachment, dissociation, and lattice enthalpies, are also discussed. Through examples and exercises, students learn how to apply these concepts to calculate enthalpies of formation and reactions.

In MOOC

Thermodynamics I

Professor J.-Ph. Ansermet from EPFL and his collaborator Dr. Sylvain Bréchet have brought together all the fundamental principles of thermodynamics in four lessons. The second part of the MOOC illustrates the thermodynamic approach through a series of applications presented by specialists from various partner institutions in the RESCIF network. The aim of the course is to help students understand and apply the fundamental concepts of thermodynamics. Following a presentation of the first and second princi

Official source

Ontological neighbourhood

Physics

Thermodynamics: Statistical mechanics

Related concepts (32)

Enthalpy

Enthalpy ˈɛnθəlpi, a property of a thermodynamic system, is the sum of the system's internal energy and the product of its pressure and volume. It is a state function used in many measurements in chemical, biological, and physical systems at a constant pressure, which is conveniently provided by the large ambient atmosphere. The pressure–volume term expresses the work required to establish the system's physical dimensions, i.e. to make room for it by displacing its surroundings.

Thermodynamics

Thermodynamics is a branch of physics that deals with heat, work, and temperature, and their relation to energy, entropy, and the physical properties of matter and radiation. The behavior of these quantities is governed by the four laws of thermodynamics which convey a quantitative description using measurable macroscopic physical quantities, but may be explained in terms of microscopic constituents by statistical mechanics.

Laws of thermodynamics

The laws of thermodynamics are a set of scientific laws which define a group of physical quantities, such as temperature, energy, and entropy, that characterize thermodynamic systems in thermodynamic equilibrium. The laws also use various parameters for thermodynamic processes, such as thermodynamic work and heat, and establish relationships between them. They state empirical facts that form a basis of precluding the possibility of certain phenomena, such as perpetual motion.

Hess's law

Hess's law of constant heat summation, also known simply as Hess' law, is a relationship in physical chemistry named after Germain Hess, a Swiss-born Russian chemist and physician who published it in 1840. The law states that the total enthalpy change during the complete course of a chemical reaction is independent of the sequence of steps taken. Hess's law is now understood as an expression of the fact that the enthalpy of a chemical process is independent of the path taken from the initial to the final state (i.

Enthalpy of vaporization

In thermodynamics, the enthalpy of vaporization (symbol ∆Hvap), also known as the (latent) heat of vaporization or heat of evaporation, is the amount of energy (enthalpy) that must be added to a liquid substance to transform a quantity of that substance into a gas. The enthalpy of vaporization is a function of the pressure at which the transformation (vaporization or evaporation) takes place. The enthalpy of vaporization is often quoted for the normal boiling temperature of the substance.

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