Reaction Rates The reaction rate during a chemical change is a

positive value that expresses the change in the quantity of a reactant or a product as a function of time

Measured in g mol mols or molLs

NOTE molLs is the same as mol(Ls)

Alexander Karen 2

Reaction Rates

Alexander Karen 3

Reaction Rates Chemical reactions occur at different rates

Slow a copper roof turns green over several years

Fast a magnesium strip burns bright white if heated by a flame

Explosive a mixture of hydrogen and oxygen explodes when exposed to an open flame

Alexander Karen 4

Reaction Rates Ex 1 Arrange the following chemical reactions from fastest to slowest

a) A piece of sodium reacts in a beaker of distilled water

b) A man fires a shot gun

c) A compost pile decomposes

Alexander Karen 5

ANSWER b a c

Factors that affect Reaction Rates Factors that affect reaction rates

Reactions involving ionic bond changes are usually more rapid than reactions involving covalent bonds

Precipitation reaction are always rapid

Increasing the concentration of the reactants usually increases the reaction rate

Increasing the surface area of the reacting substances usually increases the reaction rate

Increasing the temperature increases the reaction rate

Adding a catalyst to the reaction increases the reaction rate

Alexander Karen 6

Factors that affect Reaction Rates Note Changing the pressure on a gaseous system

changes the concentration and therefore affects rate However changing the pressure on systems that do not involve gases will NOT affect the rate

Note While a catalyst speeds up a chemical reaction without itself being used up in the reaction an inhibitor slows or stops a reaction when present

Alexander Karen 7

Reaction Rates

Fast or Slow

Alexander Karen 8

Calculating Reaction Rates Reaction rates indicate a rapid or slow change in

reactants and products

To calculate a reaction rate measure the speed at which reactants are changed and products are formed

Alexander Karen 9

Calculating Reaction Rates

Alexander Karen 10

Note the rate of reaction decreases as the reaction proceeds WHY

Calculating Reaction Rates Since the quantity of reactants decreases during a

chemical reaction the change that results is always negative

In order to make it a positive value a sign convention is used and a negative sign is added in front of this rate

Alexander Karen 11

General Reaction Rate The general reaction rate is an expression of the change

in the amount of a given substance divided by its stoichiometric coefficient as a function of time

For a reaction of the form A+BrarrC

the rate can be expressed in terms of the change in amount of any of its components

Alexander Karen 12

rA = minus Δ[A]

Δt rB = minus Δ[B]

Δt rC = Δ[C]

Δt

General Reaction Rate

Rate = r = general reaction rate [mol(Ls)] or [molLs]

a b c d = coefficients of substances involved in the reaction

ΔA ΔB ΔC ΔD = changes in concentration [molL]

Δt = change in time [s]

Alexander Karen 13

General Reaction Rate

Alexander Karen 14

NOTE d = delta = Δ

Reaction Rates

Alexander Karen 3

Reaction Rates Chemical reactions occur at different rates

Slow a copper roof turns green over several years

Fast a magnesium strip burns bright white if heated by a flame

Explosive a mixture of hydrogen and oxygen explodes when exposed to an open flame

Alexander Karen 4

Reaction Rates Ex 1 Arrange the following chemical reactions from fastest to slowest

a) A piece of sodium reacts in a beaker of distilled water

b) A man fires a shot gun

c) A compost pile decomposes

Alexander Karen 5

ANSWER b a c

Factors that affect Reaction Rates Factors that affect reaction rates

Reactions involving ionic bond changes are usually more rapid than reactions involving covalent bonds

Precipitation reaction are always rapid

Increasing the concentration of the reactants usually increases the reaction rate

Increasing the surface area of the reacting substances usually increases the reaction rate

Increasing the temperature increases the reaction rate

Adding a catalyst to the reaction increases the reaction rate

Alexander Karen 6

Factors that affect Reaction Rates Note Changing the pressure on a gaseous system

changes the concentration and therefore affects rate However changing the pressure on systems that do not involve gases will NOT affect the rate

Note While a catalyst speeds up a chemical reaction without itself being used up in the reaction an inhibitor slows or stops a reaction when present

Alexander Karen 7

Reaction Rates

Fast or Slow

Alexander Karen 8

Calculating Reaction Rates Reaction rates indicate a rapid or slow change in

reactants and products

To calculate a reaction rate measure the speed at which reactants are changed and products are formed

Alexander Karen 9

Calculating Reaction Rates

Alexander Karen 10

Note the rate of reaction decreases as the reaction proceeds WHY

Calculating Reaction Rates Since the quantity of reactants decreases during a

chemical reaction the change that results is always negative

In order to make it a positive value a sign convention is used and a negative sign is added in front of this rate

Alexander Karen 11

General Reaction Rate The general reaction rate is an expression of the change

in the amount of a given substance divided by its stoichiometric coefficient as a function of time

For a reaction of the form A+BrarrC

the rate can be expressed in terms of the change in amount of any of its components

Alexander Karen 12

rA = minus Δ[A]

Δt rB = minus Δ[B]

Δt rC = Δ[C]

Δt

General Reaction Rate

Rate = r = general reaction rate [mol(Ls)] or [molLs]

a b c d = coefficients of substances involved in the reaction

ΔA ΔB ΔC ΔD = changes in concentration [molL]

Δt = change in time [s]

Alexander Karen 13

General Reaction Rate

Alexander Karen 14

NOTE d = delta = Δ

Reaction Rates Chemical reactions occur at different rates

Slow a copper roof turns green over several years

Fast a magnesium strip burns bright white if heated by a flame

Explosive a mixture of hydrogen and oxygen explodes when exposed to an open flame

Alexander Karen 4

Reaction Rates Ex 1 Arrange the following chemical reactions from fastest to slowest

a) A piece of sodium reacts in a beaker of distilled water

b) A man fires a shot gun

c) A compost pile decomposes

Alexander Karen 5

ANSWER b a c

Factors that affect Reaction Rates Factors that affect reaction rates

Reactions involving ionic bond changes are usually more rapid than reactions involving covalent bonds

Precipitation reaction are always rapid

Increasing the concentration of the reactants usually increases the reaction rate

Increasing the surface area of the reacting substances usually increases the reaction rate

Increasing the temperature increases the reaction rate

Adding a catalyst to the reaction increases the reaction rate

Alexander Karen 6

Factors that affect Reaction Rates Note Changing the pressure on a gaseous system

changes the concentration and therefore affects rate However changing the pressure on systems that do not involve gases will NOT affect the rate

Note While a catalyst speeds up a chemical reaction without itself being used up in the reaction an inhibitor slows or stops a reaction when present

Alexander Karen 7

Reaction Rates

Fast or Slow

Alexander Karen 8

Calculating Reaction Rates Reaction rates indicate a rapid or slow change in

reactants and products

To calculate a reaction rate measure the speed at which reactants are changed and products are formed

Alexander Karen 9

Calculating Reaction Rates

Alexander Karen 10

Note the rate of reaction decreases as the reaction proceeds WHY

Calculating Reaction Rates Since the quantity of reactants decreases during a

chemical reaction the change that results is always negative

In order to make it a positive value a sign convention is used and a negative sign is added in front of this rate

Alexander Karen 11

General Reaction Rate The general reaction rate is an expression of the change

in the amount of a given substance divided by its stoichiometric coefficient as a function of time

For a reaction of the form A+BrarrC

the rate can be expressed in terms of the change in amount of any of its components

Alexander Karen 12

rA = minus Δ[A]

Δt rB = minus Δ[B]

Δt rC = Δ[C]

Δt

General Reaction Rate

Rate = r = general reaction rate [mol(Ls)] or [molLs]

a b c d = coefficients of substances involved in the reaction

ΔA ΔB ΔC ΔD = changes in concentration [molL]

Δt = change in time [s]

Alexander Karen 13

General Reaction Rate

Alexander Karen 14

NOTE d = delta = Δ

Reaction Rates Ex 1 Arrange the following chemical reactions from fastest to slowest

a) A piece of sodium reacts in a beaker of distilled water

b) A man fires a shot gun

c) A compost pile decomposes

Alexander Karen 5

ANSWER b a c

Factors that affect Reaction Rates Factors that affect reaction rates

Reactions involving ionic bond changes are usually more rapid than reactions involving covalent bonds

Precipitation reaction are always rapid

Increasing the concentration of the reactants usually increases the reaction rate

Increasing the surface area of the reacting substances usually increases the reaction rate

Increasing the temperature increases the reaction rate

Adding a catalyst to the reaction increases the reaction rate

Alexander Karen 6

Factors that affect Reaction Rates Note Changing the pressure on a gaseous system

changes the concentration and therefore affects rate However changing the pressure on systems that do not involve gases will NOT affect the rate

Note While a catalyst speeds up a chemical reaction without itself being used up in the reaction an inhibitor slows or stops a reaction when present

Alexander Karen 7

Reaction Rates

Fast or Slow

Alexander Karen 8

Calculating Reaction Rates Reaction rates indicate a rapid or slow change in

reactants and products

To calculate a reaction rate measure the speed at which reactants are changed and products are formed

Alexander Karen 9

Calculating Reaction Rates

Alexander Karen 10

Note the rate of reaction decreases as the reaction proceeds WHY

Calculating Reaction Rates Since the quantity of reactants decreases during a

chemical reaction the change that results is always negative

In order to make it a positive value a sign convention is used and a negative sign is added in front of this rate

Alexander Karen 11

General Reaction Rate The general reaction rate is an expression of the change

in the amount of a given substance divided by its stoichiometric coefficient as a function of time

For a reaction of the form A+BrarrC

the rate can be expressed in terms of the change in amount of any of its components

Alexander Karen 12

rA = minus Δ[A]

Δt rB = minus Δ[B]

Δt rC = Δ[C]

Δt

General Reaction Rate

Rate = r = general reaction rate [mol(Ls)] or [molLs]

a b c d = coefficients of substances involved in the reaction

ΔA ΔB ΔC ΔD = changes in concentration [molL]

Δt = change in time [s]

Alexander Karen 13

General Reaction Rate

Alexander Karen 14

NOTE d = delta = Δ

Factors that affect Reaction Rates Factors that affect reaction rates

Reactions involving ionic bond changes are usually more rapid than reactions involving covalent bonds

Precipitation reaction are always rapid

Increasing the concentration of the reactants usually increases the reaction rate

Increasing the surface area of the reacting substances usually increases the reaction rate

Increasing the temperature increases the reaction rate

Adding a catalyst to the reaction increases the reaction rate

Alexander Karen 6

Factors that affect Reaction Rates Note Changing the pressure on a gaseous system

changes the concentration and therefore affects rate However changing the pressure on systems that do not involve gases will NOT affect the rate

Note While a catalyst speeds up a chemical reaction without itself being used up in the reaction an inhibitor slows or stops a reaction when present

Alexander Karen 7

Reaction Rates

Fast or Slow

Alexander Karen 8

Calculating Reaction Rates Reaction rates indicate a rapid or slow change in

reactants and products

To calculate a reaction rate measure the speed at which reactants are changed and products are formed

Alexander Karen 9

Calculating Reaction Rates

Alexander Karen 10

Note the rate of reaction decreases as the reaction proceeds WHY

Calculating Reaction Rates Since the quantity of reactants decreases during a

chemical reaction the change that results is always negative

In order to make it a positive value a sign convention is used and a negative sign is added in front of this rate

Alexander Karen 11

General Reaction Rate The general reaction rate is an expression of the change

in the amount of a given substance divided by its stoichiometric coefficient as a function of time

For a reaction of the form A+BrarrC

the rate can be expressed in terms of the change in amount of any of its components

Alexander Karen 12

rA = minus Δ[A]

Δt rB = minus Δ[B]

Δt rC = Δ[C]

Δt

General Reaction Rate

Rate = r = general reaction rate [mol(Ls)] or [molLs]

a b c d = coefficients of substances involved in the reaction

ΔA ΔB ΔC ΔD = changes in concentration [molL]

Δt = change in time [s]

Alexander Karen 13

General Reaction Rate

Alexander Karen 14

NOTE d = delta = Δ

Factors that affect Reaction Rates Note Changing the pressure on a gaseous system

changes the concentration and therefore affects rate However changing the pressure on systems that do not involve gases will NOT affect the rate

Note While a catalyst speeds up a chemical reaction without itself being used up in the reaction an inhibitor slows or stops a reaction when present

Alexander Karen 7

Reaction Rates

Fast or Slow

Alexander Karen 8

Calculating Reaction Rates Reaction rates indicate a rapid or slow change in

reactants and products

To calculate a reaction rate measure the speed at which reactants are changed and products are formed

Alexander Karen 9

Calculating Reaction Rates

Alexander Karen 10

Note the rate of reaction decreases as the reaction proceeds WHY

Calculating Reaction Rates Since the quantity of reactants decreases during a

chemical reaction the change that results is always negative

In order to make it a positive value a sign convention is used and a negative sign is added in front of this rate

Alexander Karen 11

General Reaction Rate The general reaction rate is an expression of the change

in the amount of a given substance divided by its stoichiometric coefficient as a function of time

For a reaction of the form A+BrarrC

the rate can be expressed in terms of the change in amount of any of its components

Alexander Karen 12

rA = minus Δ[A]

Δt rB = minus Δ[B]

Δt rC = Δ[C]

Δt

General Reaction Rate

Rate = r = general reaction rate [mol(Ls)] or [molLs]

a b c d = coefficients of substances involved in the reaction

ΔA ΔB ΔC ΔD = changes in concentration [molL]

Δt = change in time [s]

Alexander Karen 13

General Reaction Rate

Alexander Karen 14

NOTE d = delta = Δ

Reaction Rates

Fast or Slow

Alexander Karen 8

Calculating Reaction Rates Reaction rates indicate a rapid or slow change in

reactants and products

To calculate a reaction rate measure the speed at which reactants are changed and products are formed

Alexander Karen 9

Calculating Reaction Rates

Alexander Karen 10

Note the rate of reaction decreases as the reaction proceeds WHY

Calculating Reaction Rates Since the quantity of reactants decreases during a

chemical reaction the change that results is always negative

In order to make it a positive value a sign convention is used and a negative sign is added in front of this rate

Alexander Karen 11

General Reaction Rate The general reaction rate is an expression of the change

in the amount of a given substance divided by its stoichiometric coefficient as a function of time

For a reaction of the form A+BrarrC

the rate can be expressed in terms of the change in amount of any of its components

Alexander Karen 12

rA = minus Δ[A]

Δt rB = minus Δ[B]

Δt rC = Δ[C]

Δt

General Reaction Rate

Rate = r = general reaction rate [mol(Ls)] or [molLs]

a b c d = coefficients of substances involved in the reaction

ΔA ΔB ΔC ΔD = changes in concentration [molL]

Δt = change in time [s]

Alexander Karen 13

General Reaction Rate

Alexander Karen 14

NOTE d = delta = Δ

Calculating Reaction Rates Reaction rates indicate a rapid or slow change in

reactants and products

To calculate a reaction rate measure the speed at which reactants are changed and products are formed

Alexander Karen 9

Calculating Reaction Rates

Alexander Karen 10

Note the rate of reaction decreases as the reaction proceeds WHY

Calculating Reaction Rates Since the quantity of reactants decreases during a

chemical reaction the change that results is always negative

In order to make it a positive value a sign convention is used and a negative sign is added in front of this rate

Alexander Karen 11

General Reaction Rate The general reaction rate is an expression of the change

in the amount of a given substance divided by its stoichiometric coefficient as a function of time

For a reaction of the form A+BrarrC

the rate can be expressed in terms of the change in amount of any of its components

Alexander Karen 12

rA = minus Δ[A]

Δt rB = minus Δ[B]

Δt rC = Δ[C]

Δt

General Reaction Rate

Rate = r = general reaction rate [mol(Ls)] or [molLs]

a b c d = coefficients of substances involved in the reaction

ΔA ΔB ΔC ΔD = changes in concentration [molL]

Δt = change in time [s]

Alexander Karen 13

General Reaction Rate

Alexander Karen 14

NOTE d = delta = Δ

Calculating Reaction Rates

Alexander Karen 10

Note the rate of reaction decreases as the reaction proceeds WHY

Calculating Reaction Rates Since the quantity of reactants decreases during a

chemical reaction the change that results is always negative

In order to make it a positive value a sign convention is used and a negative sign is added in front of this rate

Alexander Karen 11

General Reaction Rate The general reaction rate is an expression of the change

in the amount of a given substance divided by its stoichiometric coefficient as a function of time

For a reaction of the form A+BrarrC

the rate can be expressed in terms of the change in amount of any of its components

Alexander Karen 12

rA = minus Δ[A]

Δt rB = minus Δ[B]

Δt rC = Δ[C]

Δt

General Reaction Rate

Rate = r = general reaction rate [mol(Ls)] or [molLs]

a b c d = coefficients of substances involved in the reaction

ΔA ΔB ΔC ΔD = changes in concentration [molL]

Δt = change in time [s]

Alexander Karen 13

General Reaction Rate

Alexander Karen 14

NOTE d = delta = Δ

Calculating Reaction Rates Since the quantity of reactants decreases during a

chemical reaction the change that results is always negative

In order to make it a positive value a sign convention is used and a negative sign is added in front of this rate

Alexander Karen 11

General Reaction Rate The general reaction rate is an expression of the change

in the amount of a given substance divided by its stoichiometric coefficient as a function of time

For a reaction of the form A+BrarrC

the rate can be expressed in terms of the change in amount of any of its components

Alexander Karen 12

rA = minus Δ[A]

Δt rB = minus Δ[B]

Δt rC = Δ[C]

Δt

General Reaction Rate

Rate = r = general reaction rate [mol(Ls)] or [molLs]

a b c d = coefficients of substances involved in the reaction

ΔA ΔB ΔC ΔD = changes in concentration [molL]

Δt = change in time [s]

Alexander Karen 13

General Reaction Rate

Alexander Karen 14

NOTE d = delta = Δ

General Reaction Rate The general reaction rate is an expression of the change

in the amount of a given substance divided by its stoichiometric coefficient as a function of time

For a reaction of the form A+BrarrC

the rate can be expressed in terms of the change in amount of any of its components

Alexander Karen 12

rA = minus Δ[A]

Δt rB = minus Δ[B]

Δt rC = Δ[C]

Δt

General Reaction Rate

Rate = r = general reaction rate [mol(Ls)] or [molLs]

a b c d = coefficients of substances involved in the reaction

ΔA ΔB ΔC ΔD = changes in concentration [molL]

Δt = change in time [s]

Alexander Karen 13

General Reaction Rate

Alexander Karen 14

NOTE d = delta = Δ

General Reaction Rate

Rate = r = general reaction rate [mol(Ls)] or [molLs]

a b c d = coefficients of substances involved in the reaction

ΔA ΔB ΔC ΔD = changes in concentration [molL]

Δt = change in time [s]

Alexander Karen 13

General Reaction Rate

Alexander Karen 14

NOTE d = delta = Δ

General Reaction Rate

Alexander Karen 14

NOTE d = delta = Δ

General Reaction Rate Please also note that since

rA = minus Δ[A]

Δt

then the general reaction rate can be rewritten as

r = 1 rA = 1 rB

a b

Alexander Karen 15

General Reaction Rate ndash Example 1 Ex1 Calculate the rate of hydrogen (H2) formation for the following reaction if the concentration of ammonia goes from 020 molL to 0060 molL in 90 seconds

Alexander Karen 16

[NH3]i = 020 molL [NH3]f = 0060 molL Δt = 90s r = rH2 =

r = 1 1 1 3

Δ[NH3] Δ[CH4] Δ[HCN] Δ[H2]

1 Δ[NH3] r = = - ([NH3]f - [NH3]i) = (0060-020 molL) = 000156 mol(Ls)

Δt 90 s

Therefore the general rate of reaction (r) is 000156 mol(Ls)

General Reaction Rate ndash Example 1 Ex1 Calculate the rate of hydrogen (H2) formation for the following reaction if the concentration of ammonia goes from 020 molL to 0060 molL in 90 seconds

Alexander Karen 17

[NH3]i = 020 molL [NH3]f = 0060 molL Δt = 90s r = 000156 mol(Ls) rH2 =

r = 1 1 1 3

Δ[NH3] Δ[CH4] Δ[HCN] Δ[H2]

3 Δ[H2] r = = r H2

r H2 = 3r = 3(000156 mol(Ls)) = 000467 mol(Ls)

3

The rate of hydrogen (H2) formation is 47 x 10 sup3 mol(Ls)

General Reaction Rate ndash Sample 1 Ex 1

a) Calculate the average rate of production of H2 produced at 60 min

b) Calculate the average rate of production of H2 produced at between 20 min and 60 min

c) Calculate the rate of disappearance of HCl at 60 min

Alexander Karen 18

General Reaction Rate ndash Sample 2 Ex 2

Alexander Karen 19

Collision Theory Collision Theory explains the interactions between

reactant particles and the energy present at each stage in the evolution of a reaction as illustrated by the reaction mechanism

Note Elastic collisions result in no chemical reaction whereas with inelastic collisions reactant particles hit each other and set off a chemical reaction that transforms them into product particles

Alexander Karen 20

Collision Theory The Activation Energy is the minimum energy with

which particles must collide in order for the collision to be effective

When this is achieved the result is a rearrangement of bonds to form a new substance

The Activated Complex is the temporary unstable arrangement of particles present at the highest potential energy point in a chemical reaction step

Alexander Karen 21

Collision Theory

Alexander Karen 22

General Reaction Rate ndash Example 1 Ex1 Calculate the rate of hydrogen (H2) formation for the following reaction if the concentration of ammonia goes from 020 molL to 0060 molL in 90 seconds

Alexander Karen 17

[NH3]i = 020 molL [NH3]f = 0060 molL Δt = 90s r = 000156 mol(Ls) rH2 =

r = 1 1 1 3

Δ[NH3] Δ[CH4] Δ[HCN] Δ[H2]

3 Δ[H2] r = = r H2

r H2 = 3r = 3(000156 mol(Ls)) = 000467 mol(Ls)

3

The rate of hydrogen (H2) formation is 47 x 10 sup3 mol(Ls)

General Reaction Rate ndash Sample 1 Ex 1

a) Calculate the average rate of production of H2 produced at 60 min

b) Calculate the average rate of production of H2 produced at between 20 min and 60 min

c) Calculate the rate of disappearance of HCl at 60 min

Alexander Karen 18

General Reaction Rate ndash Sample 2 Ex 2

Alexander Karen 19

Collision Theory Collision Theory explains the interactions between

reactant particles and the energy present at each stage in the evolution of a reaction as illustrated by the reaction mechanism

Note Elastic collisions result in no chemical reaction whereas with inelastic collisions reactant particles hit each other and set off a chemical reaction that transforms them into product particles

Alexander Karen 20

Collision Theory The Activation Energy is the minimum energy with

which particles must collide in order for the collision to be effective

When this is achieved the result is a rearrangement of bonds to form a new substance

The Activated Complex is the temporary unstable arrangement of particles present at the highest potential energy point in a chemical reaction step

Alexander Karen 21

Collision Theory

Alexander Karen 22

General Reaction Rate ndash Sample 1 Ex 1

a) Calculate the average rate of production of H2 produced at 60 min

b) Calculate the average rate of production of H2 produced at between 20 min and 60 min

c) Calculate the rate of disappearance of HCl at 60 min

Alexander Karen 18

General Reaction Rate ndash Sample 2 Ex 2

Alexander Karen 19

Collision Theory Collision Theory explains the interactions between

reactant particles and the energy present at each stage in the evolution of a reaction as illustrated by the reaction mechanism

Note Elastic collisions result in no chemical reaction whereas with inelastic collisions reactant particles hit each other and set off a chemical reaction that transforms them into product particles

Alexander Karen 20

Collision Theory The Activation Energy is the minimum energy with

which particles must collide in order for the collision to be effective

When this is achieved the result is a rearrangement of bonds to form a new substance

The Activated Complex is the temporary unstable arrangement of particles present at the highest potential energy point in a chemical reaction step

Alexander Karen 21

Collision Theory

Alexander Karen 22

General Reaction Rate ndash Sample 2 Ex 2

Alexander Karen 19

Collision Theory Collision Theory explains the interactions between

reactant particles and the energy present at each stage in the evolution of a reaction as illustrated by the reaction mechanism

Note Elastic collisions result in no chemical reaction whereas with inelastic collisions reactant particles hit each other and set off a chemical reaction that transforms them into product particles

Alexander Karen 20

Collision Theory The Activation Energy is the minimum energy with

which particles must collide in order for the collision to be effective

When this is achieved the result is a rearrangement of bonds to form a new substance

The Activated Complex is the temporary unstable arrangement of particles present at the highest potential energy point in a chemical reaction step

Alexander Karen 21

Collision Theory

Alexander Karen 22

Collision Theory Collision Theory explains the interactions between

reactant particles and the energy present at each stage in the evolution of a reaction as illustrated by the reaction mechanism

Note Elastic collisions result in no chemical reaction whereas with inelastic collisions reactant particles hit each other and set off a chemical reaction that transforms them into product particles

Alexander Karen 20

Collision Theory The Activation Energy is the minimum energy with

which particles must collide in order for the collision to be effective

When this is achieved the result is a rearrangement of bonds to form a new substance

The Activated Complex is the temporary unstable arrangement of particles present at the highest potential energy point in a chemical reaction step

Alexander Karen 21

Collision Theory

Alexander Karen 22

Collision Theory The Activation Energy is the minimum energy with

which particles must collide in order for the collision to be effective

When this is achieved the result is a rearrangement of bonds to form a new substance

The Activated Complex is the temporary unstable arrangement of particles present at the highest potential energy point in a chemical reaction step

Alexander Karen 21

Collision Theory

Alexander Karen 22

Collision Theory

Alexander Karen 22

Collision Theory

The shaded area to the right of the activation energy line represents those molecules with sufficient kinetic energy to react

The greater the area to the right of the line the faster the reaction will proceed

Alexander Karen 23

Collision Theory

An increase in temperature will change the shape of the curve so that the highest point moves to the right

This results in a greater shaded area to the right of the line and therefore the reaction will proceed at a greater rate

Alexander Karen 24

Collision Theory

Addition of a catalyst lowers the activation energy which shifts the vertical activation line to the left

This results in a greater shaded area to the right of the line and therefore the reaction will proceed at a greater rate

Alexander Karen 25

Collision Theory

Alexander Karen 26

ΔH

Collision Theory Factors affecting reaction rate can now also be

explained using collision theory

The stronger the bonds the higher the activation energy

and the slower the reaction rate That is why reactions involving substances that are covalently bonded are slower than those involving ionic bonds

A higher concentration of reactants andor a greater surface area results in more collisions between molecules which results in a greater reaction rate

Alexander Karen 27

Collision Theory Factors affecting reaction rate can now also be explained

using collision theory

Raising the temperature causes molecules to move faster resulting in more collisions This also means molecules have more kinetic energy making the collisions more effective therefore increasing the reaction rate

The addition of a catalyst lowers the activation energy again making the collisions more effective therefore increasing the reaction rate

Alexander Karen 28

Collision Theory Factors affecting reaction rate can now also be explained

using collision theory

Raising the temperature causes molecules to move faster resulting in more collisions This also means molecules have more kinetic energy making the collisions more effective therefore increasing the reaction rate

The addition of a catalyst lowers the activation energy again making the collisions more effective therefore increasing the reaction rate

Alexander Karen 28