Chapter 10 - Reaction Rates + Dynamic Equillibrium Flashcards
State the collision theory
for a chemical reaction to take place the particles need to collide with each other in the correct orientation and with enough energy
What is the activation energy
• reactant particles need to overcome a minimum amount of energy
Draw a enthalpy profile for a endothermic reaction
Draw a enthalpy profile for an exothermic reaction
Effect of increased concentration on rate of reaction
• more concentrated = the greater the number of particles in a given volume of solvent
• increased collision frequency and therefore an increased rate of reaction
Effect of increased pressure on rate of reaction
• When the pressure is increased, the molecules have less space in which they can move
• number of effective collisions increases due to an increased collision frequency = increases the rate of reaction
Effect of increased temp on rate of reaction
• Increase temp = greater KE = higher collision frequency
• Greater PE = greater proportion meets activation energy = more successful collisions
What happens to rate of reaction if you double concentration
double the number of particles per unit volume and double the frequency of effective collisions
Rate of Reaction = formula
Why is the rate of the reaction not the same throughout the reaction
• During a reaction, the reactants are used up and changed into products
• This means that as the reaction proceeds, the concentration of the reactants is decreasing and the concentration of the products is increasing
Define a catalyst
• substance that increases the rate of reaction by providing the particles with an alternative mechanism with a lower activation energy = doesn’t get used up
Draw a reaction profile with two lines = one with a catalyst + one without
Two types of catalyst
o Homogeneous catalysts
o Heterogeneous catalysts
What are homogenous catalysts
the catalyst is in the same phase as the reactants
E.g. = both in solution
What are heterogeneous catalysts
catalyst is in a different phase to the reactants
E.g. - reactants are gases, but the catalyst used is a solid
What are the benefits of using a catalyst
speed up the rate of reaction = lower temperatures and pressures can be used
What are the advantages of lower pressures + temps
o save energy costs as there is reduced energy demand for providing high temperatures and less electrical pumping costs for producing the high pressures usually required
o fewer CO2 emissions from burning fossil fuels
What is the Boltzmann distribution curve
graph that shows the distribution of energies at a certain temperature
What is a key feature about a sample of gas
few particles will have very low energy, a few particles will have very high energy, but most particles will have energy in between
Particles with low energy will…
Cause ineffective collisions only as they don’t have enough energy to cause a chemical reaction
Draw a normal random Boltzmann distribution curve = just so you know shape
What does this graph show
only a small proportion of molecules in the sample have enough energy for an effective collision and for a chemical reaction to take place
Why does the line go through the origin
NO molecules with NO energy
Why does the line never meet the x axis
no maximum energy for molecules
