Kinetics Flashcards
State Boyle’s Law
The volume of a given amount of gas held at constant temperature is inversely proportional to pressure. p1V1 = p2V2
State Charle’s Law
The volume of any given mass of gas is directly proportional to its temperature at constant pressure. V1/T1 = V2/T2
State the ideal gas equation and define the terms
pV = nRT pressure in pascals or Kpa Volume in m^3 (note that L = dm^3) n = number of moles R = proportionality factor, 8.314|Jmol-1K-1 Temperature in kelvin (0 degrees C = 273.15K)
Describe an elementary reaction
A reaction is elementary if the order of the reaction = molecularity, ie the number of molecules involved in the rate determining step
State the requirements needed for a reaction to take place
Reactants, energy, collisions, bonds being formed
State how to work out theoretical reaction rate
Collision rate (ie frequency) x the fraction of molecules with enough energy to react
State how to work out theoretical reaction rate
Collision rate (ie frequency) x the fraction of molecules with enough energy to react
State the three variables that define a gas
Temperature (K), pressure (Pa) and volume (m^3)
Define isotherm
Constant temperature
Define isochore
Constant volume
State the standard conditions
1 atm (101325Pa) and 273.15K (0 degrees celcius)
Define molar volume
= V/n = RT/p. One mole of ideal gas at STP = 22.414dm^3
Give the equation to verify R using other constants and define the terms
k = R/Na
Give the equation to verify R using other constants and define the terms
k = R/Na k = boltzman’s constant R = gas constant Na = avogadro’s number
Describe 3 properties of an ideal gas
1) There are no intermolecular forces between the gas particles 2) The volume occupied by the particles is negligible compared to the volume of the container they occupy 3) The only interactions between the particles and the container walls are perfectly elastic (ie total KE is conserved)
Describe real gases
The atoms or molecules have a finite size, and at close range they interact with eachother through a varienty of intermolecular forces. For real gases, molar volume is not 22.414dm^3
Define the compression factor, z, and describe the values of z obtained
z = Vm/Vom where Vom is the molar volume for an ideal gas.
z = 1: there are no intermolecular forces. The gas can be described as an ideal gas
z < 1: Attractive forces dominate
z > 1: Repulsive forces dominate
Define Vm
Vm is the measured molar volume of a gas. Vm = V/n
Describe pressure
Pressure is force over area and is the result of molecules hitting the walls of their container
Describe the Maxwell Boltzmann distribution
- Increasing the temperature broadens the distribution and shifts the peak to higher velocities. This means that there are more ‘fast’ particles at higher temperatures, but there will still be many ‘slow’ ones as well.
- Decreasing the mass of the gas particles has the same effect as increasing the temperature i.e. heavier particles have a slower, narrower distribution of speeds than lighter particles.
Give and describe the mean speed〈𝑠〉
Since the Maxwell Boltzmann distribution is normalised, we can integrate to find the mean.
Give and describe the most probable speed
This is found by finding the turning point of the Maxwell Boltzmann distribution
Draw a Maxwell Boltzmann distribution and label the mean speed, most probable speed and root mean square speed
Give the mean square speed
This expression is due to the fact that speed is the same in all directions
Give the root mean square speed
Give the relative speed
Give the relative speed for a mixture of two gases, with masses mA and mB
μ is the reduced mass of the system, mAmB/mA+mB
