kinetics 1

Question 1

rate of reaction

Answer 1

change in concentration of a species over time, units mol dm^-3

Question 2

reaction order

Answer 2

power to which the concentration of a species is raised in the rate equation

Question 3

rate constant

Answer 3

the constant k in the rate equation

Question 4

half time

Answer 4

time take for the concentration of a species to fall by half

Question 5

rate determining step

Answer 5

the slowest step in a reaction

Question 6

factors that affect rate of reaction

Answer 6

temp

catalysts

conc.

pressure

surface area

Question 7

how does temperature affect rate of reaction?

Answer 7

as the temperature increases the particles gain more kinetic energy, this means they collide more often and when they do collide more particles have enough energy to react so the rate of reaction increases

Question 8

how do catalysts affect rate of reaction?

Answer 8

a catalyst increases the rate of reaction by offering an alternative reaction pathway with a lower activation energy. this means that more particles have energy eqqual to, or greater than, the activation energy, so more collisions are successful and the rate of reaction increases

Question 9

how does concentration affect rate of reaction?

Answer 9

increased concentration means that the particles become close together. this means that the particles collide more often so the rate of reaction increases

Question 10

how does pressure affect rate of reaction?

Answer 10

as the pressure of gaseous reactants increases the particles are closer together. this means that the particles collide more often so the rate of reaction increases

Question 11

how does surface area affect rate of reaction?

Answer 11

increasing the surface area of a solid reactant increase the rate of reaction. as the surface area increases the collision frequency increases so the rate of reaction goes up

Question 12

zero order of reaction

Answer 12

If the order of reaction with respect to a species is zero then changing the concentration of that species has no effect on the rate of reaction. The species is not involved in the rate determining step

Question 13

first order of reaction

Answer 13

if a reaction is first with respect to a species then the concentration of that species has a direct effect on the rate of reaction. if the concentration is double the rate of reaction will also be doubled.

Question 14

second order of reaction

Answer 14

if a reaction is found to be second order with respect to a species then the concentration of the species has a direct affect on the rate of reaction. if the concentration of the species is doubled the rate of reaction increases four times (2^2)

Question 15

how is the order of reaction found??

Answer 15

the order of reaction can be found using the initial rates method. In this method the experiment is carried out several times using different concentrations of the reactants and any other species that might affect the rate of reaction, such as a catalyst.

the concentrations of all species except one are kept constant and the initial rate of reaction is measured with different values of the concentration of that one species,

Any changes in the initial rate of reaction must have been caused by the change in the concentration of that particular species. this information can be used to calculate the order of reaction with respect to that species.

the experiment is repeated, with the concentration of the next species to be investigate being changed.