Chapter 12- Gas Laws And Kinetic Theory Flashcards
Pressure eq
Pressure = force/ area
Pressure unit
N/m^2 = Pa
Pascal definition
A pascal is the pressure exerted by a force of 1N acting at right angles to an area of 1m^2
A fluid is a substance that can
Flow
Both liquids and gases are
Fluids
Pressure density eq
Pressure= density x g x 🔺h
Pressure on base eq
Weight of column of water / area
Don’t forget to add on the pressure of the _____ in questions
Pressure of the atmosphere
If a liquid is stationary then the pressure must act
Equally in all directions
Boyle’s law
The pressure of a fixed mass of gas is inversely proportional to the volume, provided the temperature is constant
Boyle’s law equations
P~ 1/V
P1V1 = P2V2
If T1=T2
Isothermal def
The same temperature
Charles’ law
The volume of a fixed mass of gas is directly proportional to its absolute temperature provided the pressure is constant
Charles’ law eq
V~T
V1/T1 = V2/T2
Providing P1=P2
Pressure law
The pressure of a fixed mass of gas is directly proportional to its absolute temperature provided the volume is constant
Pressure law eq
P~T
P1/T1= P2/T2
(V1=V2)
Ideal gas equation
pV = nRT
What is R in the ideal gas equation
R= molar gas constant
= 8.31 Jmol^-1K^-1
Alternative ideal gas equation
pV = NkT
What is k in the alternate ideal gas equation.
k= Boltzmann constant
= 1.38x10^-23 JK^-1
Avogadro’s hypothesis
1 mole of gas should always occupy the same volume for a given temperature and pressure
What is standard temperature
298 K
25*C
What is standard pressure
101 kPa
Brownian motion
Random jerky motion of particles suspended in a fluid resulting from their bombardment by molecules in the fluid
Examples of Brownian motion
- pollen on water
- soot particles in a smoke cell
- bromine gas diffusion
6 assumptions for kinetic theory of gases
1) gas consists of v large number of molecules
2) move with continuous, rapid, random motion
3) collisions are always perfectly elastic
4) volume occupied by molecules is negligible compared with volume of container
5) intermolecular forces are negligible except during a collision
6) duration of collisions is negligible compared with time spent in between collisions
Kinetic model explains…
The macroscopic properties of a gas in terms of the microscopic motion of the particles
What kind of motion are gas molecules in a container
Continuous
Rapid
Random motion
How is pressure created for kinetic model of gas in container
Gas molecules moving in container
Colliding with wall of container
Change in momentum of molecule after elastic collision
Molecules exert a force per unit area on the wall
This force per unit area is pressure
Average force equation for the molecule colliding with wall over a time period
= mvx^2 / length
x= velocity in x direction l= length of the side of the cube
If there are N molecules moving with velocities vx, vx2, vx3
What is eq for the mean square speed of these velocities
= vx^2 + vx2^2 + vx3^2 / N
N molecules what is average force eq
= Nm/l (Vx^2)
What is the eq involving density and pressure
p= 1/3 ‘rho’
Mean kinetic energy eq for kinetic theory of temperature
Mean KE= 3/2 kT
All have some molecular KE at given temp
Mean KE is zero at absolute zero
More massive molecules are moving more slowly
