rates of reaction

Question 1

rate

Answer 1

change in a measurable quantity per unit time

Question 2

what is an ineffective collision

Answer 2

not useful as it produces no product

Question 3

what is an effective collision dependent on

Answer 3

correct orientation (right way around)
speed (sufficient kinetic energy equal to or greater than the activation energy of the reaction)

Question 4

pressure relationship

Answer 4

pressure is inversely proportional to volume

Question 5

pressure collision theory

Answer 5

-a higher pressure of gas,caused by the decreased volume of a container, results in a greater number of particles per unit volume
-this causes an increase in the number of collisions between reactant particles per unit time
-and therefore there is an increase in the number of effective collisions per unit time,
-an effective collision being one that has the correct orientation + sufficient kinetic energy (Ek >= Ea)
-This leads to a higher reaction rate

Question 6

surface area

Answer 6

outside contact points of a chemical

Question 7

surface area relationship

Answer 7

increased surface area, more particles exposed

Question 8

surface area collision theory

Answer 8

-an increase in surface area means a greater number of surface particles are exposed to collisions
-this causes an increase in the no. of collisions between reactant particles per unit time,
-and therefore there is an increase in the no. of effective collisions per unit time,
-an effective collision being one that has the correct orientation and sufficient kinetic energy (Ek>=Ea)
-This leads to a higher reaction rate.

Question 9

concentration relationships

Answer 9

c=n/V

Question 10

increase concentration result

Answer 10

there is no increase in fraction of particles in the sample with sufficient kinetic energy, equal to or greater than activation energy
There is a bulk increase in the number of particles, and therefore an increase in the number of particles capable of having effective collisions

Question 11

concentration collision theory

Answer 11

-An increased concentration of solution leads to a greater number of particles per unit volume( c=n/v)
-this causes an increase in the no. of collisions between reactant particles per unit time,
-and therefore there is an increase in the no. of effective collisions per unit time,
-an effective collision being one that has the correct orientation and sufficient kinetic energy (Ek>=Ea)
-This leads to a higher reaction rate.

Question 12

catalyst

Answer 12

a substance that increases the rate of the reaction but remains unchanged at the end of the reaction

Question 13

ways catalyst works

Answer 13

-lowers activation energy
-aids correct orientation and facilitates chance of reaction
-bonds to one of reactants, changes bonding- weakens forces w/in temporary transition state, making it easier for other reactant to bond, then catalyst removed

Question 14

catalyst collision theory

Answer 14

-a catalyst offers a reaction pathway of lower activation energy
-there is thus a greater proportion of particles w sufficient kinetic energy to overcome the activation energy (refer to maxwell -boltzman distribution curve)
-and therefore there is an increase in the no. of effective collisions per unit time,
-an effective collision being one that has the correct orientation and sufficient kinetic energy (Ek>=Ea)
-This leads to a higher reaction rate.

Question 15

temperature

Answer 15

measure of average kinetic energy of a substance

Question 16

temperature relationship

Answer 16

Ek = 1/2mv^2

Question 17

effect of increased temp. on maxwell curve

Answer 17

peak decreases as bigger range of kinetic energies (increase in no. of particles w Ek>= Ea

Question 18

temperature collision theory

Answer 18

-A higher temperature means that particles move w/greater velocity and have a greater average kinetic energy
-the effect of this is 2-fold
-minor: there is an increase in the no. of collisions per unit time
-major- there is a greater proportion of particles w/ sufficient Ek to overcome Ea
-and therefore there is an increase in the no. of effective collisions per unit time,
-an effective collision being one that has the correct orientation and sufficient kinetic energy (Ek>=Ea)
-This leads to a higher reaction rate.

Question 19

reaction rate

Answer 19

the change in amount or concentration per unit time of either a reactant or product
directly proportional to no. of effective collisions per unit time

Question 20

molecular collision theory

Answer 20

3.2reactant particles must collide with or have sufficient kinetic energy for successful collision. only those collisions with sufficient potential and kinetic energy equivalent to that of the activated complex will be successful, allowing for
-enough energy to break bonds OR
-gain enough energy to form activated complex OR
-activated complex is at a higher energy and is unstable

Question 21

what factors affect the rate of chemical reactions

Answer 21

the nature of reacting substances, SA of a solid, concentration of a soln, pressure of gas, catalyst and temp.

Question 22

what is the collision theory

Answer 22

model that explains that a reaction will only proceed when reactant particles collide effectively

Question 23

reaction rate relationship

Answer 23

reaction rate is directly proportional to the no. of effective collisions per unit time

Question 24

reverse reaction

Answer 24

A reaction that proceeds from the products to the reactants (using the same balanced equation).