Gases

Question 1

Kinetic molecular theory

Answer 1

• collection of particles are in constant motion
• no attraction or repulsions between molecules; they collide like billiard balls
• large amount of space between particles relative to the size of the particles themselves
• Particles move with increased speed when temp. is increased.

Question 2

Gas molecules are in ____________.

Answer 2

constant motion

Question 3

What happens when gas molecules move and strike a surface?

Answer 3

they push or exert force on a surface.

Question 4

Define pressure

Answer 4

the total amt. of force exerted by gas molecules hitting the entire surface at any one instant

Question 5

How is pressure found?

Answer 5

P=F/A
P= pressure
F= force
A= area

Question 6

How is pressure created with a gas?

Answer 6

it is the result of the constant movement of gas molecules and collisions with the surfaces around them.

Question 7

What are the factors that the pressure of a gas depends on?

Answer 7

1) the number of gas particles in a given volume
2) volume of the container
3) average speed of the gas particles

Question 8

How is air pressure measured?

Answer 8

with a barometer

Question 9

How does a barometer work?

Answer 9

A column of mercury is supported by air pressure. The force of the air on the surface of the mercury balanced by the pull of gravity on the column of mercury.

Question 10

An increase in particle in a volume of space will increase what?

Answer 10

pressure

Question 11

atm

Answer 11

atmosphere

1 atm (exactly) = 760 (exactly) mmHG = 760 torr (exactly) = 14.7 psi, lbs/in squared

Question 12

What are the common units of pressure?

Answer 12

Pascals (Pa)
Kilopascals (kPa)
Atmosphere (atm)
Millimeters of mercury (mmHg)
Inches of Mercury (inHg)
Torr (torr)
Pounds per square inch (psi, lbs./in squared)

Question 13

mmHg

Answer 13

Millimeters of mercury

1 atm (exactly) = 760 (exactly) mmHG = 760 torr (exactly) = 14.7 psi, lbs/in squared

Question 14

torr

Answer 14

Torr (unit of pressure)

1 atm (exactly) = 760 (exactly) mmHG = 760 torr (exactly) = 14.7 psi, lbs/in squared

Question 15

psi

Answer 15

Pounds per square inch

1 atm (exactly) = 760 (exactly) mmHG = 760 torr (exactly) = 14.7 psi, lbs/in squared

Question 16

Boyle’s Law

Answer 16

• Pressure of a gas is inversely proportional to its volume.
• temp is constant
• amt. of gas is constant
• as P increases V decreases by same factor
• PxV= constant

Question 17

What is the formula for Boyle’s law?

Answer 17

P1xV1=P2xV2

Question 18

According to Boyle’s law what happens when the volume a gas occupies is cut in half?

Answer 18

the pressure of the gas is doubled (as long a temperature and amt. of gas stays the same.)

Question 19

Charles’ law

Answer 19

• Volume is directly proportional to temperature
• Pressure is constant
• amt. of gas is constant
• as T increases, V increases
• V= constant x T
• TEMP IS ALWAYS MESURED IN KELVINS

Question 20

According to Charles’ law what happens to a gas when it is heated, when it is chilled?

Answer 20

When heated the gas expands and density decreases, when chilled the gas condenses and density increases.

Question 21

What is the Formula for Charles’ law?

Answer 21

V1/T1 = V2/T2

Question 22

According to Charles’ law density decreases when a gas is heated, why?

Answer 22

because the molecules have a higher kinetic energy and they have more energy to push out.

Question 23

What is the combined gas law?

Answer 23

Boyle’s law and Charles’ law put together; this law predicts what will happen to the volume of a gas when temp. and pressure changes.

Question 24

What is the formula for the combined gas law?

Answer 24

(P1)(V1)/(T1) = (P2)(V2)/(T2)

Question 25

All gas laws are only valid with __________.

Answer 25

Kelvins

Question 26

Avogadro's law

Answer 26

Volume is directly proportional to the number of gas molecules. - V= constant x n - P and T are constant - more gas molecules larger volume - number of gas molecules is counted in moles.

Question 27

What is the formula for Avogadro's law?

Answer 27

V1/n1 = V2/n2

Question 28

Ideal Gas law

Answer 28

- all the gas laws combined - R is gas constant - R depends on P and V but 0.0821 atmxL/molxK will be used - because of this P needs to be in atm and V needs to be in liters

Question 29

When is the ideal gas law used and when is the combined gas law used?

Answer 29

the ideal gas law is used when a gas is at one condition, the combined gas law is used when a gases' condition is changing.

Question 30

What is the formula for the Ideal gas law?

Answer 30

PV = nRT

Question 31

What are ideal gas conditions?

Answer 31

- high temperature - low pressure - particle size is small compared to space between particles - interactions between particles are insignificant

Question 32

What are Real (non-ideal) gas conditions?

Answer 32

- low temp - high pressure - particle size is signif. compared to space btwn. particles - interactions btwn. particles are signif.

Question 33

What is partial pressure?

Answer 33

Each gas in a mixture exerts a pressure independent of the other gases in a mixture. The pressure of a component gas in a mixture is called a partial pressure. The sum of all the partial pressures is equal to the total pressure.

Question 34

Dalton's Law of partial pressure

Answer 34

P total = P gas A + P gas B + P gas C + ....

Question 35

How do you find a partial pressure?

Answer 35

multiply the total pressure of a gas mixture by the percent turned into a decimal of the fractional component of the mixture. P He = (0.800)(1.0 atm) = 0.80 atm (The component gas = percent divided by 100) to get decimal

Question 36

What partial pressure of O2 are our bodies adapted to breath?

Answer 36

0.21 atm

Question 37

hypoxia

Answer 37

low oxygen levels in blood; partial pressures of O2 less than 0.1 will lead to hypoxia, unconsciousness or death

Question 38

When climbers are climbing mt. Everest they need O2 cylinders to prevent what?

Answer 38

hypoxia

Question 39

When you feel the pressure of air what is felt?

Answer 39

one pressure; not individual pressures

Question 40

The higher the percentage of a gas in a mixture the more it ______ to total pressure of the mixture.

Answer 40

contributes

Question 41

Standard conditions

Answer 41

- keeping conditions the same | - STP

Question 42

STP

Answer 42

Standard temp. and pressure. | -standard pressure 1.00 atm -standard temp. 273 K 0 degrees C

Question 43

How much volume will one mole of any gas at STP occupy?

Answer 43

22.4 L (THIS IS CALLED MOLAR VOLUME) and can be used as a conversion factor. As long as work is done at STP 1 mol = 22.4 L

Question 44

Molar volume

Answer 44

There is so much room between molecules in the gaseous state that volume is not effected by the size of molecules (under ideal conditions).