Avogadro’s Law describes the relationship between the volume of gas and the amount of gas present. For an ideal gas, the volume and number of moles of gas are directly proportional if the temperature and pressure are constant. Thus, this explains why equal volumes of all gases (regardless of their differing chemical properties) are composed of the same number of molecules.
Avogadro’s Gas Law is commonly written as:
V is the volume of the gas
k is a constant
n is the amount of substance of gas measured in moles.
For example, one mole of molecular oxygen, with molecular weight of 32 g/mole will occupy 22.4 L of volume. While, one mole of molecular hydrogen, with molecular weight of 2 g/mole (1/16 of the weight of oxygen) also occupies 22.4 L of volume. Since volume is proportional to the number of moles, then doubling the number of moles to 2 moles each will cause these gases to occupy 44.8 L each.
Avogadro’s Gas Law has been used in conjunction with the Combined Gas Law to form the Ideal Gas Law, which still considers volume and moles together, but it also includes the new variables of temperature of pressure. Thus, understanding Avogadro’s Law is crucial to understand how the volume of a gas behaves with respect to a change of amount, and by extension its function in the Ideal Gas Law.
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