CHEM 24112 Lecture Notes - Lecture 35: Ideal Gas, Torr, Kinetic Theory Of Gases

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CHEMISTRY 112 – DAY 35 Chapter 13: Sections 7-8

4/16/18

KINETIC MOLECULAR THEORY and GAS LAW PRACTICE

Scientific Method

A law is a generalization of observed behavior.

Laws are useful – We can predict behavior of similar systems.

A model can never be proved absolutely true.

A model is an approximation and is destined to be modified.

So far we have considered “what happens,” but not “why.”

In science, “what” always comes before “why.”

Postulates of the Kinetic Molecular Theory

1. Gases consist of tiny particles (atoms or molecules).

2. The particles are so small, compared with the distances between them that the volume (size) of the

individual particles can be assumed to be negligible (zero).

3. The particles are in constant random motion, colliding with the walls of the container. These collisions

with the walls cause the pressure exerted by the gas.

4. The particles are assumed not to attract or to repel each other.

5. The average kinetic energy of the gas particles is directly proportional to the Kelvin temperature of the

gas.

Meaning of temperature

Kelvin temperature is directly proportional to the average kinetic energy of the gas particles.

Relationship between Pressure and Temperature

Gas pressure increases as the temperature increases because the particles speed up.

Relationship between Volume and Temperature

Volume of a gas increases with temperature because the particles speed up.

Use the Gas Laws to solve the following problems:

PV = nRT

(where R = 0.08206 L·atm/mol·K, the universal gas constant)

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Document Summary

A law is a generalization of observed behavior. Laws are useful we can predict behavior of similar systems. A model can never be proved absolutely true. A model is an approximation and is destined to be modified. So far we have considered what happens, but not why. Gases consist of tiny particles (atoms or molecules). The particles are so small, compared with the distances between them that the volume (size) of the. 2. individual particles can be assumed to be negligible (zero). The particles are in constant random motion, colliding with the walls of the container. 3. with the walls cause the pressure exerted by the gas. The particles are assumed not to attract or to repel each other. The average kinetic energy of the gas particles is directly proportional to the kelvin temperature of the. Kelvin temperature is directly proportional to the average kinetic energy of the gas particles.

Related Questions

Newton had an incorrect theory of gases in which he assumed that all gas molecules repel one another and the walls of their container. Thus, the molecules of a gas are statically and uniformly distributed, trying to get as far apart as possible from one another and the vessel walls. This repulsion gives rise to pressure. Explain why Charles’s law argues for the kinetic-molecular theory and against Newton’s model.

pearmoose136

I have reached the surface, but too quickly, so I had to use the dry decompression chamber. In the dry decompression chamber, I had some time to think and imagine. I really thought I saw small gas molecule floating around. Fill-in the postulates of the Kinetic Molecular Theory below.

The Postulates:

I.The total volume in which the gas is contained is mostly _____________ space. The ___________ of the gas is negligible.

II.Gas molecules are in continuous _____________ _____________ in all directions.

III.Energy is _____________ from one molecule to another, but the total energy remains _____________ at a constant temperature.

IV.Molecules of a gas neither_____________ or _____________ each other.

V.The average KE of gas particles depends only on the absolute _____________ of the gas

Nowâ¦ Match each postulate them to the observational statements below by putting the corresponding Roman numeral in front of each statement

1) ______The gas molecules didnât really seem interested in each other

2) ______They never seemed to lose energy, no matter how many times they bumped into each other

3) ______I couldnât believe we could actually breathe, considering there seemed to be so few molecules.

4) ______They even seemed to move faster when they got nearer to me.

5)( ______The molecules seemed to have no rhyme or reason in their movements

M 121 1 201 Ideal Gas Law (PV n Experiment to T ) Determine the Ideal Gas Constant R 1. Conduct basic measurements, measurement , mathematical calculations and conversions for of volume, pressure, and temperature: calculate percent error and account for sources of error in an e xperimental result name and by following safety proced ty experiments for a redox reaction by using equipment identifiable by form chemical calculations using mass, mole and volumes and idenify limitatios of measuring devices in order to state the uncertainty/significant figures in measurements and calculation results. 5. Demonstrate a proficiency in relating the chemistry of gases to everyday phenomenon. Introduction Molecules in gases have very little attraction for one another, because relative to their size, they are so far apart from each other. For this reason we can often assume that a gas behaves "idcally." meaning that the physical behavior of the gas is independent of the composition of the gas. If a gas behaves ideally, then its physical properties can be described by the Ideal Gas Equation: Let's consider why the variables in the ideal gas equation have the relationships expressed in Equation 1aã The ideal gas equation assumes that there are no attractive forces between gas molecules. One can picture two billiard balls bouncing off one another in a totally clastic collision. If these molecules are placed in a balloon the collisions will occur not only with each other but also with the wall of the balloon, causing the balloon to expand. This expansion can be measured as a volume (V). More molecules will cause more collisions and thus more expansion. Therefore the quantity of molecules or number of moles (n) is directly proportional to the volume, and thus volume and number of moles appear on opposite sides of the equation. Another factor to consider is the kinetic energy of these molecules. Kinetic energy is related to the temperature (T) of the molecules, in that the kinetic energy. If the collisions with the wall of the balloon are happening at a very high speed due to high kinetic energy, the collisions will be harder and more frequent and thus the wall of the balloon will be pushed out further (a larger volume) than if the kinetic energy were less. The result is that volume is also directly proportional to the temperature. This relationship is seen in Equation la with (T) on the right side of the equation and (V) on the left. higher the temperature the greater the considered. While the molecules inside the balloon are pushing the balloon out, there are also molecules in thea Finally the pressure of the outside environment (atmospheric pressure) needs to be 59

CHEM 24112 Lecture Notes - Lecture 35: Ideal Gas, Torr, Kinetic Theory Of Gases

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