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×The ideal gas constant is also known as the universal gas constant or the molar gas constant or simply the gas constant. It is a very important constant in chemistry and physics. It is denoted as *R*. The dimension of the gas constant is expressed in energy per unit mole per unit temperature. The value of the gas constant in SI unit is 8.314 J mol^{−1} K^{−1}. The gas constant has the same unit as of entropy and molar heat capacity.

Derivation of Ideal Gas Equation from Kinetic Theory of Gases

Ideal gas equation is *PV* = *nRT*. This equation can easily be derived from the combination of Boyle’s law, Charles’s law, and Avogadro’s law. But here, we will derive the equation from the kinetic theory of gases. The kinetic theory of gases is a very important theory which relates macroscopic quantities like pressure to microscopic quantities like the velocity of gas molecules. This equation is applicable only for ideal gases, but be approximated for real gas under some conditions.

The Ideal gas law is also known as general gas law. As the name states the law is applicable under the ideal conditions, not to real gases. The law correlates the pressure, volume, temperature, and amount of gas. It was first formulated by French physicist Émile Clapeyron in 1834.

The Boltzmann constant is a very important constant in physics and chemistry. The constant relates the average kinetic energy of molecules of a gas with thermodynamic temperature. The Boltzmann constant is denoted as *k*_{B} or *k*. The dimension of the Boltzmann constant is energy per thermodynamic temperature. The SI unit is J K^{−}^{1}, which is the same as of entropy. The value of the Boltzmann constant is 1.380 649 × 10^{−}^{23} J K^{−}^{1}.

Graham's Law of Diffusion and Effusion

Graham's law of diffusion (or Graham's law of effusion) is a law that expresses the relationship between the rate of diffusion or effusion to molar masses of particles. This empirical law was stated by Scottish chemist Thomas Graham in 1848. He established the relationship through experiments.

Dalton's Law of Partial Pressures

Dalton's law is also known as the law of partial pressure or Gibbs-Dalton law (rarely). The law describes the relationship between the total pressure of a mixture of non-reacting ideal gases and the partial pressures of each individual component. Dalton's law is valid for ideal gases. The law is similar to Amagat's law of additive volumes.

An amagat is a unit of number density. It is similar to Loschmidt constant which is the molecular density quoted at STP (*T* = 273.15 K, *P* = 1 atm). 1 amagat is defined as the number of molecules of an ideal gas per unit volume at STP. 1 amagat is equivalent to Loschmidt constant. The symbol used for amagat is amg or Am (rarely). It is a non-SI unit.

The number is named after Émile Hilaire Amagat. He was a French physicist and also known for Amagat’s law of additive volume.

Amagat's Law of Additive Volumes

Amagat's law of additive volumes is the law of partial volumes. The law relates the total volume of a mixture with the volumes of individual components. Amagat's law is very similar to Dalton's law of partial pressure. The law is only valid for ideal gases. The law is named after Emile Amagat who was a French Physicist. He published his law of partial volumes in 1880.

The Loschmidt constant is also called as the Loschmidt number. The symbol used for the Loschmidt constant is *n*_{0}. It is the number of molecules of an ideal gas per unit volume. The Loschmidt constant has the unit of the reciprocal cubic metre. At STP (*P* = 1 atm, *T* = 273.15 K), The value of the constant is 2.686 781 1 × 10^{25} m^{−3}. The constant is a measure of number density.

The Avogadro constant or (the Avogadro number earlier) is the number of elementary units in one mole of any substance. The Avogadro constant is denoted as *N*_{A}. It has the dimension of the reciprocal amount of substance (mol^{−1}). The approximate value of *N*_{A} is 6.022 × 10^{23} mol^{−1}. This means one mole of any substance contains 6.022 × 10^{23} elementary particles. The Avogadro constant is named after Italian scientist Amedeo Avogadro.

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