physical

• boyles law relates pressure to volume

  p = k/v (where k is a constant)
• charles's law relates volume to temperature
• gay-lussac also worked relating volume to temperature
• gay-lussac found K
• higher pressures occupy lower volumes
• gas takes up 0 volume ( impossible ik) at -273 C
• K = C + 273
• avogadro's law relates volume to the number of moles of gas
• avogadro proved the the proportionality constant was the same for all gases
• equal volumes of gas contain equal number of molecules at the same t and p
• volume depends on number of molecules and hence number of moles not the nature or size of the molecules
• the ideal gas law is pV = nRT
• R is the universal gas constant
• STP is 0C (273K ) and 1 atm
• gas density = mass of one mole/ volume of one mole
• (P1 *V1)/T1= (P2* V2)/T2
• 1m ^3 = 1000l
• Assumptions if the IGL

  gas particles always moving

  volume of particles is negligble

  particles only react through random collisions

  pressure is caused be particles colliding with the walls of the vessel (exp Boyle law)

  temperature is related to average translational kinetic energy of particles (exp charles law)
• Kinetic Theory links temperature and average molecular speed
• If the temperature is known the average speed of molecules can be calculated through

  v- = sqrt(3RT/mw)
• Maxwell-Boltzmann distribution graph shows that there is a greater distribution of speed at higher temperatures
• it takes a long time for molecules to travel because they keep bumping into other molecules
• Lambda is the average distance between collisions
• mean free path is related to gas viscosity and is given by the equation

  lambda = (n/p) x sqrt(3RT/mw)

  gas visc x average speed
• molecules move by translating, rotating and vibrating. (in an --> degree of freedom)
• atoms can only translate
• molecules can rotate and vibrate
• rotation and vibration in molecules stores heat energy without increasing the total kinetic energy (and so temperature)
• degrees of freedom (movement) increase as the temperature increases
• to calculate the kinetic energy of a monatomic gas

  U(t-ranslational) = 3RT/2
• temperature is a measure of the average kinetic energy of the molecules
• molar heat capacity is the heat required to increase the temperature of of one mole of a substance by 1K
• the equation for molar heat capacity is

  C(v - constant volume) = (deltaU(tot))/(deltaT)
• a molecule with N atoms has 3N degrees of freedom
• everything has 3 translational modes (X,Y,Z)
• linear molecules have 2 rotational modes
• non-linear molecules have 3 rotational modes
• once translational and rotational modes are counted and remaining modes must be vibrational
• heat capacity = R/2 x no. of active modes (X J K^-1 mol ^-1)
• energy chemical system spontaneously tends towards equilibrium