Flashcards in Unit 7 Deck (21):

1

## atmospheric pressure

###
-results from the mass of the air being pulled toward the center of the earth by gravity - in other words, it results from the weight of the air

-it varies with altitude (less air is pushing down at high altitude)

2

##
standard atmosphere =

###
-760 mmHg (millimeter of mercury)

-760 torr

-101,325 Pa (pascal)

-29.92 in Hg

-147. lb/in 2

3

## pressure=.....

### force/area

4

##
Boyle’s Law

###
-an INVERSE relationship between pressure and volume (pressure goes up, volume goes down)

-PV= k [k is a constant] or

5

##
Charles's Law

###
-volume of a gas at constant pressure increases linearly with the temperature of the gas (temperature is heated, the volume is greater)

-the volume of each gas is DIRECTLY proportional to temperature and extrapolates to zero when the temperature is 0 K

-V= Tb [T is kelvins, b is proportionally constant]

or V/T

6

##
Avogadro's Law

###
-for a gas at constant temperature and pressure, the volume is DIRECTLY proportional to the number of moles of gas (volume decreases, fewer molecules)

-V=an [V is the volume of gas, n is the number of moles of gas particles, a is a proportionality constant]

or V/n

7

## K = ....

###
C + 273

8

##
Ideal gas law

###
-Pv=nRT

-equation of state for a gas, where the state of the gas is its condition at a given time

-it is based on experimental measurements of the properties of gases

-it applies best at pressures smaller than 1 atm

-when you are dealing with changes in states in a problem, you place the variables that change on one side of the equal sign and the constants on the other

IN KELVIN and ML and KPA

9

##
A state of gas

###
described by its pressure, volume, temperature, and number of moles

10

##
Dalton’s Law of Partial Pressures

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-For a mixture of gases in a container, the total pressure exerted is the sum of the pressures that each gas would exert if it were alone

-WHEN YOU ARE DEALING WITH MIXTURE OF GASES, THE NUMBER OF MOLE PARTICLES MATTERS, INSTEAD OF IDENTITY OR COMPOSITION OF THE INVOLVED PARTICLES

11

##
partial pressure

###
the pressure that a particular gas would exert if it were alone in the container

12

##
mole fraction

###
-the ratio of the number of moles of a given component in a mixture to the total number of moles in the mixture

-the mole fraction of each component in a mixture of ideal gases is directly related to its partial pressure ---> X1 =n1/nTOTAL =P1/PTOTAL

the partial pressure of a particular component of gaseous mixture is the mole fraction of that component times the total pressure (P1=X1 PTOTAL)

13

##
kinetic molecular theory (KMT)

###
1. The particles are so small compared with the distances between them that the volume of the individual particles can be assumed to be negligible (zero)

2. The particles are in constant motion. The collisions of the particles with the walls of the container are the cause of the pressure exerted by the gas.

3. THe particles are assumed to exert no forces on each other; they are assumed neither to attract nor to repel each other.

4. The average kinetic energy of a collection of gas particles is assumed to be directly proportional to the Kelvin temperature of the gas.

-real gases do not conform to these assumptions

-these postulates explain ideal gas behavior

14

## molar volume

###
liter/mols

22.4 liters/mol

15

##
Pressure and Volume (Boyle’s Law)

###
-volume goes down, pressure does up

-if there is a decrease in volume, the gas particles will hit it more often, creating more pressure

-PV= k [k is a constant]

16

##
Pressure and Temperature

###
-pressure is directly proportional to temperature

-when temperature increases, the speed of particles increase, the particles hit the wall with greater force and frequency

-since the volume is the same, the gas pressure would increase

17

##
Volume and Temperature (Charles's Law)

###
-volume is directly proportional to temperature

-when gas is heated, molecules speed up and hit walls harder and more often

-to keep the pressure constant, increase the volume of the container

-V= bT [T is kelvins, b is proportionally constant]

V/T

18

##
Volume and Number of Moles (Avogadro's Law)

###
-volume of a gas at constant temperature and pressure depends on number of particles

-increase in gas particles then increase in volume is only way to keep pressure and temperature constant

-V=an [V is the volume of gas, n is the number of moles of gas particles, a is a proportionality constant]

v/n

19

## how many psi

### 14.7 psi

20

## 1 atm (Hg)

### 760 mn Hg

21