Gas Laws: Understanding The Ideal Gas Law

which law can be derived from the ideal gas law

The ideal gas law, also known as the general gas equation, combines several simple gas laws, including Boyle's Law, Charles' Law, and Avogadro's Law. It describes the behaviour of gases under varying conditions of pressure, volume, temperature, and the number of molecules or moles. The ideal gas law can be used to calculate changes in these variables and is derived from the kinetic theory of gases, which assumes that gas molecules are in constant, random motion, with negligible volume, and only experience elastic collisions. This law is a useful approximation for understanding real gases, despite its idealised assumptions.

lawshun

Boyle's Law

The law can be derived from the kinetic theory of gases, which assumes that the gas consists of a large number of molecules that are in random motion and obey Newton's laws of motion. It also assumes that the volume of the molecules is negligible compared to the volume occupied by the gas, and that no forces act on the molecules except during elastic collisions of negligible duration.

The law was derived through experiments with air, which Boyle considered to be a fluid of particles at rest between small invisible springs. Boyle used a closed J-shaped tube and poured mercury from one side, forcing the air on the other side to contract under the pressure of the mercury. This experimental setup allowed Boyle to demonstrate the inverse relationship between pressure and volume.

lawshun

Charles' Law

Charles's Law, also known as the law of volumes, is an experimental gas law that describes how gases tend to expand when heated. The law was named after scientist Jacques Charles, who formulated the original law in his unpublished work in the 1780s. The French natural philosopher Joseph Louis Gay-Lussac confirmed the discovery in a presentation to the French National Institute on 31 January 1802, although he credited the discovery to Charles.

Charles's Law can be stated as follows: when the pressure on a sample of a dry gas is held constant, the volume will be directly proportional to the Kelvin temperature. This relationship of direct proportion can be written as: V ∝ T. This means that as the temperature increases, the volume of the gas also increases in proportion. Conversely, a decrease in temperature will lead to a decrease in volume.

The ideal gas law, also called the general gas equation, is the equation of state of a hypothetical ideal gas. It was first stated by Benoît Paul Émile Clapeyron in 1834 as a combination of the empirical Boyle's Law, Charles's Law, Avogadro's Law, and Gay-Lussac's Law. Charles's Law is a special case of the ideal gas law and can be derived from the kinetic theory of gases under the assumption of a perfect (ideal) gas. Measurements show that at constant pressure, the thermal expansion of real gases at sufficiently low pressure and high temperature, conforms closely to Charles's Law.

The kinetic theory of gases relates the macroscopic properties of gases, such as pressure and volume, to the microscopic properties of the molecules that make up the gas, particularly their mass and speed. To derive Charles's Law from kinetic theory, a microscopic definition of temperature is required, which can be defined as the temperature being proportional to the average kinetic energy of the gas molecules.

lawshun

Avogadro's Law

\$V = k \times n \: \: \: \text{and} \: \: \: \frac{V_1}{n_1} = \frac{V_2}{n_2}\>

Where \(n\) is the number of moles of gas and \(k\) is a constant. This law is evident in everyday situations, such as blowing up a balloon. The volume of the balloon increases as you add more moles of gas by blowing into it.

lawshun

Gay-Lussac's Law

Gay-Lussac also contributed to other gas laws, which are sometimes collectively referred to as "Gay-Lussac's Law." One such law states that all gases expand the same at constant pressures, indicating that all gases have the same mean thermal expansivity under constant pressure and temperature conditions. Gay-Lussac is also credited with formulating a law regarding the combining volumes of gases, which he announced in 1808 and published in 1809. This law states that when gases chemically react, they do so in volume ratios that are simple whole numbers, calculated at the same temperature and pressure.

Gay-Lussac's work, along with the empirical laws of Boyle, Charles, and Avogadro, contributed to the development of the ideal gas law, also known as the general gas equation. This law describes the behaviour of real gases under most conditions and is expressed as PV = nRT, where P represents pressure, V volume, n the number of moles, R the universal gas constant, and T the absolute temperature.

lawshun

Kinetic theory of gases

The kinetic theory of gases is a classical model that explains the thermodynamic behaviour of gases. It treats gas as a large number of particles (atoms or molecules) that are too small to be seen with a microscope and are in constant, random motion. The theory explains the relationship between the macroscopic properties of gases, such as volume, pressure, and temperature, by considering the motion and composition of these particles.

The theory was first laid out by Daniel Bernoulli in his 1738 work "Hydrodynamica". In it, he argued that gases consist of a great number of molecules moving in all directions and that their impact on a surface causes the pressure of the gas. However, Bernoulli's theory was not immediately accepted, partly because the conservation of energy had not yet been established, and the idea of perfectly elastic collisions between molecules was not obvious to physicists.

The kinetic theory of gases makes several assumptions. Firstly, it assumes that gas particles are much smaller than the average distance between them and that the volume of the gas molecules is negligible compared to the volume occupied by the gas. Secondly, it assumes that these particles are in constant, rapid motion and are colliding with each other and the walls of their container. These collisions are assumed to be perfectly elastic, with no loss of kinetic energy.

The kinetic theory of gases has been further developed and refined over the years. For example, the Boltzmann equation, formulated by Ludwig Boltzmann in the late 19th century, provided a framework for predicting the transport properties of dilute gases. Additionally, the kinetic theory of gases was used to derive the ideal gas law, which combines several other gas laws, including Boyle's law, Charles's law, Avogadro's law, and Gay-Lussac's law. The ideal gas law describes the behaviour of real gases under most conditions and can be used to calculate changes in pressure, temperature, volume, or the number of molecules in a given volume.

Accounting as a Pre-Law: A Smart Choice?

You may want to see also

Frequently asked questions

The ideal gas law, also known as the general gas equation, is an equation of state of a hypothetical ideal gas. It describes the behaviour of real gases under most conditions.

The ideal gas law is a combination of Boyle's Law, Charles' Law, Avogadro's Law, and Gay-Lussac's Law. It can also be derived from the kinetic theory of gases.

The formula for the ideal gas law is PV = nRT, where P is the pressure, V is the volume, T is the temperature, n is the number of moles of the gas, and R is the universal gas constant.

Written by
Reviewed by

Explore related products

Share this post
Print
Did this article help you?

Leave a comment