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**Chapter 11 ("down and dirty or condensed soup version"))**

Gases

Unpolluted air at sea level 78% N2

21% O2

1% Argon

trace CO2 and H20

The air we breathe is composed of the above mixture!!!

Nature of Gases

1. Gases fill a container completely.

2. Gases are compressible.

3. Gases have a low density D=Mass

Volume

Gas 1g/L

Liquid 2g/mL

4. Gases exert a uniform pressure on all inner surfaces of a container because they completely fill the container.

**Pressure What is it?**

Pressure is the force exerted on a unit area.

Pressure exerted by the atmosphere or the earth is called atmospheric pressure.

**Units of Pressure**

1 atm = 760 mmHg = 760 torr = 1.01325 x 105 Pascal

Pascal is the SI unit for pressure.

1 atm = 14.96 psi (pounds per square inch)

***example 11.1 pg 365 **

Barometer measures atmospheric pressure

Manometer measures pressure of an enclosed gas.

**Kinetic molecular theory of Gases** (Briefly explains Ideal Gas behavior)

1. Gas consists of tiny, non-interacting particles that are very far apart

2. Gas particles are in constant random motion

3. When gas particles collide with the walls of a container pressure is produced

4. Average Kinetic energy of these particles is proportional to the Kelvin temperature.

Boyle’s Law

P1 V1 = P2 V2 (n and T are constant)

Boyles law continued.

The volume of a fixed amount of gas at a given temperature is inversely proportional to the applied pressure.

***Example 11.2 pg 369 **

Charles Law

V1 = V2

T1 T2 (n and P are constant)

The volume of a fixed amount of gas is directly proportional to its **Kelvin temperature** as long as the pressure is kept constant. If temperature is given in Celsius you must convert to Kelvin before you start the problem.

***Example 11.3 pg 374 **

**Combined Gas Law (n is constant ) n= number of moles**

P1V1 = P2V2

T1 T2

**Example 11.4 pg 376 **

Avogadro’s law

Equal volumes of any two gases at the same temperature and pressure contain equal moles of molecules.

Standard Temperature and Pressure or **STP is defined as 0o C and 273 K and a pressure of 1 atm or 760mmHg**

At STP ,the volume of 1 mole of any gas has been shown by experiment to be 22.4 L.

32 grams of O2 = 1 mole = 22.4 L

2 grams of H2 = 1 mole = 22.4 L

1 mole = 6.022 x 1023 molecules = 22.4 L

molar volume of a gas is 22.4 L

molar mass of 22. 4 L is the molecular wt in grams of 1 mole = H2 =2grams

Ideal Gas Law

P V = n R T

**R = molar gas constant 0.08206 L . atm/(K . mol) will always be given in this class**

n = moles

P = pressure (atm)

V = volume (L)

T = temperature in Kelvin

***Example 11.6 pg 381**

**Mixture of Gases **

**Dalton’s law of partial pressure**

The sum of the partial pressures of each of the components in a gas mixture must equal the total pressure.

Ptotal = PN2 + PO2 +PAR

Ptotal = 0.78 atm + 0.21atm + 0.01atm

= 1.0 atm

***Example 11.9 pg 386 **