Kc and equilibrium

• "Steric factor" is just a complex phrase to describe how the location of a collision is important
• Collision theory is the theory of how reactions happen
• Area under graph represents the total number of molecules on a Maxwell-boltzman graph
• Average energy lies to the right of the peak on a Maxwell-boltzman graph
• The tail of the graph shows there is a small probability of having a very high energy molecule on a Maxwell-boltzman graph
• Peak shows the most likely energy of any molecule on a Maxwell-boltzman graph
• Origin Is passed through as no molecules have zero energy on a Maxwell-boltzman graph
• Maxwell-Boltzmann distribution of energies is a graph showing the energy distribution of all the molecules in the gas phase.
• heating does increase the average energy of the molecules.

  • We see that heating the reaction moves the maximum to the right.
  • But it also lowers the number of particles with that energy.
• line doesn't touch X axis as odd molecules may have exceptionally high energies
• if concentration is increased, pattern of line will be the same but area under graph increases
• increasing concentration increases rate as there are more particles leading to more collisions, more successful collisions per unit time
• temp has exponential effect on rate, increasing temp gives particles more kinetic energy, move faster, more collisions per unit time, more particles exceed activation energy so many more successful collisions per unit time
• catalysts work by providing an alternative mechanistic route with lower Ea
• catalysts spread thinly on an inert honeycomb shaped support medium to maximise efficiency and reduce cost
• le chateliers principle= if there's a change in a reversible reaction the equilibrium will shift to counteract the change
• if volume of container is increased at equilibrium, pressure will decrease
• catalysts do not effect equilibrium position as they speed up forwards and backwards reaction by the same rate
• temp used in haber process is 450- lower temp favours NH3 production
• pressure used by haber process is 200 atm- high pressure favours NH3 production, can't go too high due to safety concerns
• Iron catalyst used in Haber process
• Hydrogen is produced by natural gas with steam (CH4+H2O=CO+3H2 at 1100, slight pressure, Ni cat) Nitrogen from fractional distillation of liquid air
• NH3 used in fertilisers such as ammonium nitrate/sulphate
• ethanol can be produced via fermentation or hydration of ethene from crude oil (phosphoric acid cat)
• max yield of ethanol obtained at high pressure, low temperature, excess steam
• high pressure causes ethene to polymerise to polyethene, high cost of building plant and energy to run, low temp means low rate of reaction, too much steam dilutes catalyst
• compromised conditions of ethanol is 570K, 650KPa, conversion is 5%
• production of methanol is CO+2H2=CH3OH, it is a major chemical feed stock (starting material for all other chemicals)
• compromise conditions of methanol are 500K, 10000KPa, Cr2O3 cat, 5-10% yield
• making H2SO4 S+O2=SO2. 2SO2+O2=2SO3 SO3+H20=H2SO4 450, 1-2ATM
• Kc is a value that describes the position of the equilibrium for a reaction at a given temperature
• K values are unchanged providing temperature remains unchanged
• when temp increases in an exothermic reaction, Kc will decrease
• when temp increases in an endothermic reaction, Kc will increase
• when Kc is large, equilibrium position lies to right
• when Kc is small, equilibrium position lies to left
• The exception to the hydrogen oxidation state rule is NaH, where hydrogen has an oxidation state of -1