maxwell-boltzmann distributions

what must occur for a reaction to take place?

a collision in the correct orientation w/ a minimum amount of E_K (the E_A)

draw the general shape of a Maxwell-Boltzmann distribution:

what is the area under a Maxwell-Boltzmann distribution = to?

total number of molecules

why does the curve of a Maxwell-Boltzmann distribution start at 0?

no molecules have 0 energy

what does the peak of a Maxwell-Boltzmann distribution curve represent?

most likely energy of any single molecule

where is the mean energy of all the molecules on a Maxwell-Boltzmann distribution curve?

a point slightly right to the peak/most likely energy

where is the E_A on a Maxwell-Boltzmann distribution curve?

(towards bottom of curve on RHS)

how will the shape of the Maxwell-Boltzmann distribution change if the temperature is increased? why?

• curve shifts to right and peak lowers (area stays the same as total no. of molecules is =)

• because a greater proportion of molecules have at least the E_A and are able to react

how will the shape of the Maxwell-Boltzmann distribution change if the temperature is decreased? why?

• curve shifts left and peak gets higher (area stays the same as total no. of molecules is =)

• because a fewer proportion of molecules have at least the E_A and are able to react

how will the shape of the Maxwell-Boltzmann distribution change if the concentration is increased? why?

• peak gets higher - area increases

• more molecules available to collide in a given volume and more molecules w/ energies > E_A

how will the shape of the Maxwell-Boltzmann distribution change if the concentration is decreased? why?

• peak gets lower - area decreases

• fewer molecules available to collide in a given volume and fewer molecules w/ energies > E_A

how will the Maxwell-Boltzmann distribution change w/ the addition of a catalyst? why?

• no change in shape

• but E_A lowered so moves slightly left of curve

• as more molecules have energies at or higher than E_A