HOW TO DETERMINE RATE OF REACTION

FROM GRAPH

AVERAGE RATE OF

REACTION

INSTANTANEOUS RATE OF REATION

AVERAGE RATE OF REACTION

For the whole exp

From X

min to Y min

On the X min (2nd) ( from 2nd to 1st)

For first x

(3) min( from 0 to

3rd )

INSTANTANEOUS RATE OF REACTION

( rate of reaction at that time) Draw tangent to the

graph

Y

X

Rate = Y/X

b) Example from the graph, determine:i) The rate of reaction at 120 s

Instantaneous rate of reaction= Draw tangent to the graph

= 56 – 20 = 0.176 cm3 s-1

222-18

Changes to the graph

Changes to the CURVE part of graph

II

IIII

Volume of gas

Time

• Use positive catalyst• Increase temperature •Increase total surface area

Use negative catalyst

Decrease temperature

Decrease TSA

Changes to the FLAT part of graph

d) Curve I represents the result of the experiment using excess zinc powder and 50cm3 of 1.0 moldm-3 dilute hydrochloric acid

II

IIII

Volume of gas/ cm3

Time/s

• Use positive catalyst• Increase temperature of reactant

Lower concentration of hydrochloric acid

Collision theory

• Theory that explains how factors affect rate of reaction

• Before reaction can occur, particles must first collide

• Particles collide so that bonds are broken and new bonds can form

Collision theory

• Collision of particles must be effective collisions to produce result

• Effective collisions are collisions which – produce enough energy to overcome

energy of activation– correct orientation

Collision theory

• Activation energy is the minimum energy the colliding particles must overcome so that reaction occur

• In order for particles to overcome the activation energy, several factors involve

How factors affect rate of reaction according to collision theory

• Size of reactant for solid reactant• Temperature of reactant mixture• Concentration of solution reactant• Presence of catalyst

How Collision theory explain factor of size of solid reactant

• The smaller the size of reactant, the larger the total surface area

• Frequency of Collisions between particles increase

• Frequency of Effective collisions between particles increase

• Therefore rate of reaction also increase

How Collision theory explain factor of concentration

• The higher the concentration of reactant solution, the higher the number of particles per unit volume

• Frequency of Collisions between particles increase

• Frequency of Effective collisions between particles increase

• Therefore rate of reaction also increase

How Collision theory explain factor of temperature

• The higher the temperature of reactant solution, the higher the kinetic energy of particles

• Frequency of Collisions between particles increase

• Frequency of Effective collisions between particles increase

• Therefore rate of reaction also increase

Collision theory explain factor of catalyst

• Presence of catalyst provide an alternative path

• This alternative path has a lower activation energy

• More colliding particles can overcome this lower activation energy

• Frequency of Effective collisions between particles increase

• Therefore rate of reaction also increase