Gases

Question 1

what does the kinetic-molecular theory describe?

Answer 1

it is a model for describing the behaviour of gases, based on specific assumptions of ideal gases

Question 2

describe the ideal gas model:

Answer 2

1) no volume
2) constant and random motion, all collisions are elastic
3) no intermolecular forces
4) average kinetic energy of the molecules is directly proportional to the absolute temperature

Question 3

what is pressure of gases caused by?

Answer 3

molecules striking the walls and each other

Question 4

what is zero degrees Celsius in Kelvins?

Answer 4

273.15K

Question 5

what is the SI unit for pressure?

Answer 5

pascal, P (N/m^2)

Question 6

101.3kPa is also equal to:

Answer 6

760 mmHg=760 torr=1 atm

Question 7

Standard Temperature and Pressure (STP)

Answer 7

temperature = 273.15K and pressure = 1 atm

Question 8

what is the equation for the Ideal gas law?

Answer 8

PV=nRT

Question 9

universal gas constant R

Answer 9

0.0821 L atm/ K mol

Question 10

Charles’s Law

Answer 10

if the pressure is constant, the volume is proportional to the temperature. thus the gas will expand when heated and contract when cooled

Question 11

Boyle’s Law

Answer 11

if the temperature is constant, pressure is inversely proportional to volume

Question 12

if the volume is constant, pressure is ______ to temperature

Answer 12

proportional

Question 13

when does the combined gas law apply?

Answer 13

when n (the amount of gas) stays constant

Question 14

Avogadro’s law

Answer 14

equal volumes of different gases at the same temperature and pressure contain the same number of particles

Question 15

standard molar volume

Answer 15

the volume that one mole of any gas (ideal gas) occupies at STP

Question 16

what is the standard molar volume?

Answer 16

22.4 L

Question 17

under what conditions do the laws of ideal gases deviate from behaviour of real gases?

Answer 17

low temperatures and high pressures

Question 18

describe the deviations of real gases from ideal gas behaviour

Answer 18

1. intermolecular forces causes pressure to decrease
2. particles have volume so that the free space available decreases (V real decreases) unless very high pressure which causes V to increase due to repulsions

Question 19

van der Waals equation

Answer 19

accounts for differences in the observed behaviour of real gases and calculated properties of ideal gases

Question 20

what are the two constants in the van der Waals equation and what do they depend on?

Answer 20

a= intermolecular force of the gas

b=weight/size of the gas

Question 21

partial pressure

Answer 21

in a mixture of gases, the pressure that just one gas exerts

Question 22

Dalton’s law of partial pressures

Answer 22

the total pressure is simply the sum of the partial pressures of all the constituent gases

Question 23

effusion

Answer 23

the escape of a gas molecule through a very tiny hole that is comparable in size to the molecules themselves into an evacuated region

Question 24

in an effusion experiment, what does the rate of gas effusion depend on?

Answer 24

how fast the molecules move, which in turn depend on speed (kinetic energy is the same due to temperature, but speed is not the same, depend on mass of gas)

Question 25

Graham’s law of effusion

Answer 25

ratio of rate of effusion of gas A over B is equal to the square root of molar mass of B over molar mass of A

Question 26

for one gas, what is the trend of average speed as the temperature increases?

Answer 26

average speed increases due to increased kinetic energy