# CHE 102 Lecture Notes - Lecture 1: Combined Gas Law, Gas Constant, Reaction Rate Constant

This

**preview**shows half of the first page. to view the full**2 pages of the document.**what are the properties of gases?

1. gases can be compressed or expanded

-gas molecules are far apart

-gases exert pressure on what is holding them

-gases expand into volume that is available

-gases diffuse or mix into one-another

-a gas is described in terms of: temp., pressure, volume, moles

what does PV = nRT stand for?

Pressure x Volume = # ofmoles x gas constant x temperature

what is the rate constant in PV = nRT?

rate constant = 0.0821

what are the effects on pressure if:

1. you add more moles of gas...

2. increase temperature...

3. decrease the volume...

1...more collisions and increase pressure

2...more velocity, more collisions, and increase pressure

3...more collisions and increase pressure

PV = nRT measurements?

Pressure: 760mmHg = 1.0 atm

volume: Liters

moles: moles

temperature: kelvin (Celsius + 273 = K)

combined gas law equation?

when do we use the combined gas law?

1. when we are given three variables and are asked to find the fourth

2. combined gas law equation use this when given one condition and asked to calculate

one of the variables at a new set of conditions

Example problem:

-determine the pressure of a gas (in atm) if 2.5 moles occupy 40 liters at 32 degrees

celsius...

answer: 1.6atm

Example problem:

-a gas originally at 25C and 1.5 atm pressure has its temperature raised to 50C what is

the new pressure of the gas...

answer: 1.6atm

Example problem:

-determine volume in liters of 1 mole of gas at 1 atm pressure and 0C...

answer: 22.4L

Example problem:

-2.5L of a gas at 1.7atm pressure expands to a volume of 4.2L. what is the new

pressure of the gas...

answer: 1.0 atm

Review: how do you calculate moles?

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