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Diffusion, STP, and Ideal Gas Law. 12-10-09. Diffusion. Diffusion – movement of particles from a region of higher density to a region of lower density; this is caused by the random motion of molecules. What happens if I release open a container filled with green gas?.

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Diffusion, STP, and Ideal Gas Law

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## Diffusion, STP, and Ideal Gas Law

12-10-09

### Diffusion

• Diffusion – movement of particles

from a region of higher density to a

region of lower density; this is caused by the random motion of molecules

What happens if I release open a container filled with green gas?

### Dalton’s law of partial pressures

• Dalton’s Law of Partial Pressure – the total pressure of a mixture of gases is equal to the sum of the partial pressures of the component gases

Ptotal = PA + PB + PC …

B

A

C

A

In this cylinder, which type of gas molecule will have the highest partial pressure?

A

A

B

B

B

C

A

A

B

C

Molecule A

### Practice Partial pressures

• If the partial pressure of A is 6 atm (PA = 6), the partial pressure of B is 5 atm (PB = 5), and the partial pressure of C is 3 atm (PC = 3), what is the total pressure of the container?

### Derive ideal gas law

• Variables

• Pressure

• Temperature

• Volume

• Number of Molecules (Moles)

What happens to the pressure when we change these?

Increase Temperature = Increase Pressure

Increase Volume= Decrease Pressure

Increase Moles = Increase Pressure

### Ideal gas law

• Ideal Gas – gas in which molecules keep the exact same speed after collisions. In other words, friction does not slow them down

• Can approximate most gases as ideal

• PV = nRT

• P = Pressure

• V = Volume

• n = number of moles

• R = Ideal Gas Constant

• T = temperature

### Ideal gas constant

• R = Ideal Gas Constant

• R = 8.314

• R = 0.0821

### Review: celsius and kelvin

• Celsius to Kelvin

• TK = TC + 273

• Kelvin to Celsius

• Tc = TK - 273

The temperature in Kelvin is always bigger than the temperature in Celsius!!

TK > TC

### Standard temperature and pressure

• Because gases are easily affected by temperature and pressure changes, we need a standard pressure and temperature to refer to

• Standard Temperature and Pressure (STP)

• Temperature = 0 degrees C

• Pressure = 1 atm

### Standard Temperature and Pressure & Ideal gas law

• Let’s use PV=nRT to find the volume of 1.00 mol of an ideal gas at STP.

• P = 1 atm

• V = ?

• n = 1.00 mol

• R = 0.0821

• T = 0 degrees celsius + 273 Kelvin = 273 Kelvin

### More ideal gas Problems

• What pressure has a container with 1.20 moles of gas, 14.88 L, and 25 degrees Celsius?

### More Ideal Gas Problems

• A balloon has a volume of 15.9 L, 149 kPa, and a temperature of 28 degrees C. How many moles of gas are in the balloon?