Kinetic-molecular theory postulates

To explain the gas laws, the kinetic-molecular theory postulates that an... 

The kinetic-molecular theory postulates that gas particles have no volume, move in straight-line paths between elastic (energy-conserving) collisions, and have average kinetic energies proportional to the absolute temperature of the gas. 

Ans. The gas laws work for unbonded atoms as well as for multiatom molecules, and so it is convenient to classify the unbonded atoms as molecules. If these atoms were not classified as molecules, it would be harder to state the postulates of the kinetic molecular theory. For example, postulate 1 would have to be stated "Molecules or unbonded atoms are in constant random motion. ... 

B) Review the postulates of the kinetic molecular theory of gases, which are listed on page 58. 

A gas that obeys these five postulates is an ideal gas. However, just as there are no ideal students, there are no ideal gases only gases that approach ideal behavior. We know that real gas particles do occupy a certain finite volume, and we know that there are interactions between real gas particles. These factors cause real gases to deviate a little from the ideal behavior of the Kinetic Molecular Theory. But a non-polar gas at a low pressure and high temperature would come pretty close to ideal behavior. Later in this chapter, we ll show how to modify our equations to account for non-ideal behavior. 

Before we leave the Kinetic Molecular Theory (KMT) and start examining the gas law relationships, let s quantify a couple of the postulates of the KMT. Postulate 3 qualitatively describes the motion of the gas particles. The average velocity of the gas particles is called the root mean square speed and is given the symbol rms. This is a special type of average speed. 

C—This is a basic postulate of kinetic molecular theory. 

Kinetic energy is the energy of motion. Gas particles have a lot of kinetic energy and constantly zip about, colliding with one another or with other objects. The picture is complicated, but scientists simplified things by making several assumptions about the behavior of gas pcirticles. These assumptions are called the postulates of the kinetic molecular theory. They apply to a theoretical ideal gas ... 

Beginning with these assumptions, it s possible not only to understand the behavior of gases but also to derive quantitatively the ideal gas law (though we ll not do so here). For example, let s look at how the individual gas laws follow from the five postulates of kinetic-molecular theory ... 

The behavior of gases can be accounted for using a model called the kinetic-molecular theory, a group of five postulates ... 

This chapter is the first of two devoted to specific states of matter, and in it you will focus your attention on the gaseous state of matter. However, all of the states will be described within a larger framework that looks at the state of matter as a series of interrelated factors, including kinetic energy (or temperature), pressure, and intermolecular forces. Gases are usually described by a series of postulates known as kinetic molecular theory, which constitute the ideal gas law. To begin the chapter, you will look at a historical development of the ideal gas law, during which you will review some of the equations used to create the ideal gas law. 

The kinetic-molecular theory consists of five postulates about gases. These postulates are assumptions from which gas behavior is explained. Everything discussed so far in this chapter is consistent with kinetic-molecular theory. The five postulates of the theory are ... 

C) This statement is correct. The sulfur hexafluoride molecule has a much larger volume than the other molecules and is much more likely to experience molecular attractions than the other two molecules. These two factors will make this molecule most likely to deviate from the key postulates in the kinetic-molecular theory (size of the molecule is negligible and molecular attractions are negligible). 

The kinetic molecular theory consists of these postulates ... 

Several gas laws have been introduced in this chapter, but no explanation as to why those laws apply to all gases has been proposed. This section introduces the kinetic molecular theory of gases, which explains the gas laws and when extended, also explains some properties of liquids and solids. Five postulates explain why gases behave as they do ... 

A. Which postulate of the kinetic molecular theory explains why gases expand to fill their containers ... 

The kinetic molecular theory explains the behavior of gases in terms of characteristics of their molecules. It postulates that gases are made up of molecules that are in constant, random motion and whose sizes are insignificant relative to the total volume of the gas. Forces of attraction between the molecules are negligible, and when the molecules collide, the collisions are perfectly elastic. The average kinetic energy of the gas molecules is directly proportional to the absolute temperature (Section 12.10). 

An example of this type of model is the kinetic molecular theory, a simple model that attempts to explain the properties of an ideal gas. This model is based on speculations about the behavior of the individual gas particles (atoms or molecules). The postulates of the kinetic molecular theory can be stated as follows ... 

The fourth postulate of the kinetic molecular theory is that the average kinetic energy of the particles in the gas sample is directly proportional to the temperature in Kelvins. Thus, since (KE)avg °c T, we can write... 

We have seen that the postulates of the kinetic molecular theory, combined with the appropriate physical principles, produce an equation that successfully fits the experimentally observed properties of gases as they approach ideal behavior. Two phenomena involving gases provide further tests of this model. 

Using postulates of the kinetic molecular theory, give a molecular interpretation of Boyle s law, Charles s law, and Dalton s law of partial pressures. 

This equation shows that the absolute temperature is directly proportional to the average molecular kinetic energy, as postulated by the kinetic-molecular theory. Because there are molecules in a mole, the left-hand side of this equation is equal to the total kinetic energy of a mole of molecules. 

Until now our discussions have dealt with ideal behavior of gases. By this we mean that the identity of a gas does not affect how it behaves, and the same equations should work equally well for all gases. Under ordinary conditions most real gases do behave ideally their P and V are predicted by the ideal gas laws, so they do obey the postulates of the kinetic-molecular theory. According to the kinetic-molecular model, (1) all but a negligible volume of a gas sample is empty space, and (2) the molecules of ideal gases do not attract one another because they are so far apart relative to their own sizes. 

Under some conditions, however, most gases can have pressures and/or volumes that are not accurately predicted by the ideal gas laws. This tells us that they are not behaving entirely as postulated by the kinetic-molecular theory. 

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