The **key difference between Gay-Lussac’s law and Avogadro’s law** is that Gay-Lussac’s law indicates that the volume of a gas is directly proportional to the temperature of the gas, whereas Avogadro’s law states that the volume of a gas is directly proportional to the number of molecules in the gas.

Gay-Lussac’s law describes the varying of the pressure of a particular mass of a gas directly with the absolute temperature of the gas upon constant volume. Avogadro’s law is an experimental gas law that states that the volume of a gas is related to the amount of substance gas present in a given sample.

### CONTENTS

1. Overview and Key Difference

2. What is Gay-Lussac’s Law

3. What is Avogadro’s Law

4. Gay-Lussac’s Law vs Avogadro’s Law in Tabular Form

5. Summary – Gay-Lussac’s Law vs Avogadro’s Law

## What is Gay-Lussac’s Law?

Gay-Lussac’s law describes the varying of the pressure of a particular mass of a gas directly with the absolute temperature of the gas upon constant volume. It is sometimes named Amonton’s law. We can give a mathematical expression for this law as follows:

**P/T = k**

In this equation, P refers to the pressure, t refers to the absolute temperature, and k is a constant. We can say that this is a special case of ideal gas law.

A derivative of this law is the Pressure-temperature law, which describes the relationship between the pressure and temperature of a certain mass of a gas at a constant volume.

According to the law of combining volumes, gases react with each other by means of volume, and they react in simple whole number ratio at constant temperature and pressure conditions. In other words, the ratio between the volumes of the reactant gases and the gaseous products can be given in simple whole numbers. Gay Lussac was one of the first scientists to discover this relationship, which led to the derivation of Avogadro’s law.

## What is Avogadro’s Law?

Avogadro’s law is an experimental gas law that states that the volume of a gas is related to the amount of substance gas present in a given sample. It is also named Avogadro’s hypothesis or Avogadro’s principle. This is a specific form of ideal gas law. This law was named after Amedeo Avogadro in 1812.

According to modern descriptions, Avogadro’s law states that equal volumes of all gases which are in an equal temperature and pressure condition have the same number of molecules. For example, equal volumes of hydrogen gas and nitrogen gas consist of an equal number of atoms when these two gases are in the same temperature and pressure. Practically, real gases show small deviations from the ideal gas behaviour where the law holds only approximately accurate. However, it is still an important approximation for scientists. Mathematically, the law is as follows:

**V/n = k**

Where V is the volume of the gas, n is the amount of substance of the gas in the sample, and k is a constant value given for a particular temperature and pressure.

## Difference Between Gay-Lussac’s Law and Avogadro’s Law

Gay-Lussac’s law and Avogadro’s law are two important gas laws. The key difference between Gay-Lussac’s law and Avogadro’s law is that Gay-Lussac’s law indicates that the volume of a gas is directly proportional to the temperature of the gas, whereas Avogadro’s law states that the volume of a gas is directly proportional to the number of molecules in the gas.

The following table summarizes the difference between Gay-Lussac’s law and Avogadro’s law.

## Summary – Gay-Lussac’s Law vs Avogadro’s Law

Gay-Lussac’s law and Avogadro’s law are two important gas laws. The key difference between Gay-Lussac’s law and Avogadro’s law is that Gay-Lussac’s law indicates that the volume of a gas is directly proportional to the temperature of the gas, whereas Avogadro’s law states that the volume of a gas is directly proportional to the number of molecules in the gas.