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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
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