chemistry module 3 reaction rates

what is collision theory

states that for a chemical reaction to take place, the particles need to collide with each other in the correct orientation and with enough energy

what happens when more collisions take place

the number of particles with energy greater than the Ea increases, this causes an increase in the rate of reaction

what is activation energy

minimum amount of energy required for a reaction to start

correlation between energy in exothermic reactions

reactants higher in energy than the products

correlation with energy and endothermic reactions

reactants lower in energy than products

is the activation energy larger in endothermic or exothermic reactions

endothermic

what must happen for a collision to be effective

the reactant particles must collide in the correct orientation and possess a minimum energy equal to the Ea of that reaction

concentration def

number of particles in a given volume of solvent

what happens to rate of reaction when you increase the concentration

causes an increase in collisions so increase in rate of reaction

what happens to the rate of reaction when the pressure is increased

the molecules have less space so theres more collisions so rate of reaction increases.

what happens to the rate of reaction when temperature increases

the kinetic energy of the particles increases so they move faster and collide more which increases the rate of reactions

how to calculate rate of reaction

change in amount of reactants and products / time

how can rate of reaction during the reaction be calculated

from a concentration-time graph

what should you do when taking measurements from a concentration-time graph

keep the temperature constant as change in temp will change the rate of reaction

what is a catalyst

a substance that increases the rate of reaction by providing the particles with an alternative pathway with a lower activation energy

what are the two types of catalyst

homogenous and heterogenous

what is a homogenous catalyst

the catalyst is in the same state as the reactants

what is a heterogenous catalyst

when the catalyst is in a different state as the reactants

what are the benefits of catalysts

lowers energy cost as theres a reducd energy demand for providing high temperatures and less electrical pumping costs for providing the high pressures usually required. fewer co2 emisions. catalysts can enable different reactions to be used with better atom economy and with reduced waste

what is the maxwell boltzmann distribution curve

graph that shows the distribution of energies at a certain temperature

what does the boltzmann distribution graph show

only a small proportion of molecules in the sample have enough energy for an efective collision and for a chemical reaction to take place

why should the energy distribution go through the origin

because there are no molecules with no energy

why should the energy distribution never meet the x axis

there is no maximum energy for molecules

what does the area underneath the curve represent

the total number of particles present

how does temperature effect the boltzmann distrubution curve

with higher temperature, the boltzmann distribution curve flattens and the peak shifts to the right

how do catalysts affect the boltzmann distribution curve

a greater number of molecules with have the activation energy so the rate of catalysed reaction is increases compared to the uncatalysed reaction