Ideal gas law.

The ideal gas law is the equation of state of a hypothetical ideal gas. It is a good approximation to the behavior of many gases under many conditions, although it has several limitations. It was first stated by É mile Clapeyron in 1834 as a combination of Boyle's law and Charles's law. The ideal gas law is often introduced in its common form:

PV = nRT

where

P is the absolute pressure of the gas,

V is the volume of the gas,

n is the amount of substance of gas (measured in moles),

R is the ideal, or universal, gas constant, and

T is the absolute temperature of the gas.

This equation is called ideal gas law equation.

In SI units, P is measured in pascals (Pa), V is measured in cubic metres (m³), n is measured in moles, and T in Kelvin (273.15 Kelvin = 0.00 degrees Celsius). R has the value 8.314 J·K^{− 1}·mol^{− 1} or 0.08206 L·atm·mol^{− 1}·K^{− 1} or ≈ 2 calories if using pressure in standard atmospheres (atm) instead of pascals, and volume in liters instead of cubic metres.

How much gas is present could be specified by giving the mass instead of the chemical amount of gas. Therefore, an alternative form of the ideal gas law may be useful. The chemical amount (n) (in moles) is equal to the mass (m) (in grams) divided by the molar mass (M) (in grams per mole):

By replacing n with m/M,

and subsequently introducing density ρ = m/V, we get:

Dalton’s Law of Partial Pressures.

A mixture of gases follows the same laws as a gas composed of only one substance. Dalton’s law of partial pressures enables us to consider the properties of each component of a gas mixture.

In a mixture of gases, each gas has a partial pressure which is the hypothetical pressure of that gas if it alone occupied the volume of the gas mixture at the same temperature ( The pressures of the individual components of a mixture are called partial pressures ). The total pressure of an ideal gas mixture is the sum of the partial pressures of each individual gas in the mixture.

In chemistry and physics, Dalton's law (also called Dalton's law of partial pressures) states that in a mixture of non-reacting gases, the total pressure exerted is equal to the sum of the partial pressures of the individual gases.

This empirical law was observed by John Dalton in 1801 and is related to the ideal gas laws. Mathematically, the pressure of a mixture of non-reactive gases can be defined as the summation: P_total = p₁ + p₂ + …+ p_n, where p₁, p_2, …, p_n represent the partial pressure of each component.