Avogadro postulate

In 1811, Avogadro postulated what is now known as Avogadro s law Equal volumes of gases, at equal temperatures and pressures, contain the same number of molecules. You will learn more about Avogadro s law in Unit 4. 

In Chapter 2 we noted that in 1811 the Italian chemist Avogadro postulated that equal volumes of gases at the same temperature and pressure contain the same number of particles. This observation is called Avogadro s law, which can be stated mathematically as... 

We can use these postulates to rationalize the various gas laws (Table 17.2). For Boyles Law, pressure decreases with increasing volume because the impact of gas particles against the walls of the container is spread out (diluted) over a greater area. For Charles s Law, volume increases with increasing temperatures because faster-moving particles demand more room. Similarly, for Avogadro s Law, volume increases with an increasing number of particles because more particles also demand more room. 

As we noted as the beginning of Chapter 5, one of the barriers to accepting Avogadro s postulate was the implication that molecules such as oxygen and hydrogen contained two identical atoms which were held together by some force. We are now in a position... 

In 1800, chemists did not know that the elementary gases were diatomic, and they wondered how two molecules of HCl were formed from one molecule of H and one of Cl. The law of combining volumes led Amedeo Avogadro (1776-1856) to postulate in 1811 a hypothesis that equal volumes of gases under like conditions of temperature and pressure contain equal numbers of molecules. The fact that molecules of hydrogen and chlorine had to be diatomic stemmed from this generalization. 

Gay-Lussac did not theorize on his experimental findings, but in 1811 shortly after their publication the Italian chemist Amedeo Avogadro used them to formulate an important postulate since known as Avogadro s hypothesis ... 

Chemical equation (13.1) will retain its validity if both sides are multiplied by any number we wish, since all that is then postulated is a number of similar, concurrent reactions. If we choose to multiply both sides of equation (13.1) by the number of molecules in a kilogram-mole, N k = 6.023 x 10 (Avogadro s number x 1000), then we have ... 

Amedeo Avogadro (1776-1856) (Fig. 3.35) postulated (in 1811) that equal volumes of all gases, at the same temperature and pressure, contain identical numbers of particles (molecules). The molecules of elementary gases, e.g., oxygen, hydrogen, and chlorine, he says, consist of two (or perhaps a multiple of... 

Use the postulates of the kinetic molecular theory (KMT) to explain why Boyle s law, Charles s law, Avogadro s law, and Dalton s law of partial pressures hold true for ideal gases. Use the KMT to explain the P versus n (at constant V and T) relationship and the P versus T (at constant V and n) relationship. 

In the early 19th century (1803), Dalton proposed his atomic theory. In 1811, Amedeo Avogadro made clear the distinction between atoms and molecules of elementary substances, hi addition, the concepts of heat, energy, work, and temperature were developed. The first law of thermodynamics was set forth by Julius Robert von Mayer and the second law of thermodynamics was postulated by Rudolf Julius Emanuel Clausius and William Thomson (Lord Kelvin). Later in the century, Clausius, Ludwig Boltzmarm, and James Clerk Maxwell related the ideal gas law in terms of a kinetic theory of matter. This led to the kinetics of reactions and the laws of chemical equilibrium. 

Notice that Equation 5.18 contains within it Boyle s law (P XjV) and Avogadro s law (y n). We can get the complete ideal gas law from postulate 2 of the kinetic molecular theory, which states that the average kinetic energy (5 mv ) is proportional to the temperature in kelvins (T) ... 

Lorenzo Romano Amadeo Carlo Avogadro, 1776-1856, was an Italian lawyer and professor of natural philosophy. He was the first to postulate that equal volumes of gases under the same conditions contained the same number of molecules. 

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