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TOPIC 1 RATE OF REACTION.pptx
1. TOPIC 1
RATE OF REACTION
CERTIFICATES OF HEALTH SCIENCE
CS1064 CHEMISTRY II
MDM SITI BAINUN BINTI MOHD DALI
2. TABLE OF CONTENT:
1. UNDERSTANDING OF RATE OF REACTION
2. FACTORS AFFECTING RATE OF REACTION
3. COLLISION THEORY
4. APPLICATION OF RATE OF REACTION
3. Learning Outcome:
At the end of this lecture, students should be able to:
Explain the meaning of the rate of reaction and solve the numerical problems
based on the average and instantaneous rate of reaction.
Describe factors affecting rate of reaction.
Describe collision theory and explain activation energy.
Explains with examples the application of factors that affect the rate of
reaction in daily life
5. 1. UNDERSTANDING OF RATE OF REACTION
Rate of reaction is defined as the change in the
amount of reactants or products per unit time
It is a measure of how fast a reaction occurs
Fast reaction = rate of reaction is high
Slow reaction = rate of reaction is low
A fast reaction taken slower time for the reaction
to complete
6. DIFFERENCES BETWEEN FAST REACTION
AND SLOW REACTION
FAST REACTION SLOW REACTION
Time taken for reaction is short Time taken for reaction is long
Rate of reaction is high Rate of reaction is low
Example:
Cooking chicken using microwave oven
Striking a match
Ripening of tomatoes
Example: a piece of paper turning
yellow
Rusting of water pipe
7. 1.1 FINDING AVERAGE RATE OF REACTION
Rate of reaction is a measure of how fast reaction occur, or how the reactant/
product change in a period of time.
Therefore, the formula can be:
Rates of reaction=
Quantity of change of reactants/products
Total time for the reaction
unit for rate of reaction:
g s-1 or g minute-1
cm3 s-1 or cm3 minute-1
mol dm-3 s-1 or mol dm-3 minute-1
8. 1.1 FINDING AVERAGE RATE OF REACTION
Example:
In a chemical reaction, 2.5g of calcium carbonate react completely with excess
of hydrochloric acid to produce 600cm3 of carbon dioxide gas in 1.5 minutes.
Find the reaction in term of:
a. Decreasing mass of calcium carbonate
b. Increasing volume of carbon dioxide gas produced
Rates of reaction=
Quantity of change of reactants/products
Total time for the reaction
9. 1.1 FINDING AVERAGE RATE OF REACTION
Example:
a. Decreasing mass of calcium carbonate
Quantity of change of reactants = 2.5g of calcium carbonate
Total time for the reaction = 1.5 minutes
Rates of reaction=
Quantity of change of reactants/products
Total time for the reaction
Rates of reaction=
2.5g
1.5 minutes
= 0.027 g/s
10. 1.1 FINDING AVERAGE RATE OF REACTION
Example:
b. Increasing volume of carbon dioxide gas produced
Quantity of change of products = 600cm3 of carbon dioxide gas
Total time for the reaction = 1.5 minutes
Rates of reaction=
Quantity of change of reactants/products
Total time for the reaction
Rates of reaction=
600cm3
1.5 minutes
= 6.7 cm3/s
11. 1.1 FINDING AVERAGE RATE OF REACTION
During the chemical reaction, TWO (2) things happen:
1. Quantity of reactant reduce
2. The quantity of products increase
Therefore, the rate of reaction can be determine by :
Measuring the decrease amount of the reactants over time
Measuring the increase amount of the products over time
However, the quantity (or change) of the
reactants/products may be measurable or immeasurable
The easily measured quantity changes include:
Mass
Concentration (conductivity)
Volume of gas
12. Example:
Reaction between calcium carbonate and hydrochloric acid
The rate of reaction can be determine by :
a. Measuring the decrease amount of the reactants over time
b. Measuring the increase amount of the products over time
13. EXAMPLE:
In a reaction, 5g of calcium carbonate takes 250 seconds to completely react
with solution of hydrochloric acid. Calculate the average rate for this reaction in
units: [relative atomic mass: C=12; O=16; Ca=40]
a. g/s
b. mol/s
14. 1.2 FINDING AVERGAE RATE OF REACTION
FROM IMMEASURABLE QUANTITIES
In some reaction, some changes are observable but difficult to be
measured. For example:
Change of colour
Precipitation
The time taken for the colour of a reactant to change colour or
certain amount of precipitate to form can be used to measure the
rate of reaction.
If the quantity change is immeasurable:
Rates of reaction=
1
Total time for the reaction
15. EXAMPLE:
When the aqueous of ethanoic is mixed with acided potassium manganate (vii),
the reaction happen slowly at room temperature. The colour purple of the
solution is bleached after 25 seconds. Calculate the average rate of reaction:
16. 1.3 GRAPH OF PRODUCT/REACTANT
CHANGE AGAINST TIME
In chemical reaction,
The reactants will decrease over time
The product will increase over time
The rate of reaction will decrease over time owing to
the decrease in concentration and total surface area
of reactants
In a graph of quantity of product/ reactant over time,
the rate of reaction is equal to the gradient of the
graph.
17. EXAMPLE 1
The reaction between dilute hydrochloric acid and
excess marble will produce calcium chloride and gas
of carbon dioxide.
Sketch the graph of
a. the mass of the marble against time.
b. the volume of carbon dioxide against time.
c. the concentration of hydrochloric acid against time.
d. the concentration of calcium chloride against time.
18. Answer:
a. the mass of the marble against time
b. the volume of carbon dioxide against
time.
c. the concentration of hydrochloric acid against
time.
d. the concentration of calcium
chloride against time
19. Example 2:
In a reaction between
calcium carbonate and liquid
hydrochloric acid, carbon
dioxide gas that is released
is collected in a burette. The
graph shows the volume of
carbon dioxide collected
over time. Find the average
rate of reaction in the first
60s.
21. 1.4 FINDING INSTANTANEOUS RATE OF
REACTION FROM A GRAPH
The rate of reaction changes from time to time as the reaction happens.
The rate of reaction at a particular time is called the instantaneous rate.
The instantaneous rate of a reaction is equal to the gradient of tangent at a
particular time
22. Example:
The graph shows the volume of carbon dioxide gas released over time in a
chemical reaction. Find the rate of reaction at t = 40s.
25. Factors Affecting the Rate of Reaction
1. Size of the reactant (solid only)
2. Concentration of the reactant (solution
only)
3. Temperature of the reactant
4. Presence of catalyst in the reactant
5. Pressure of the reactant (gas only)
26.
27.
28. Characteristics of catalyst
A catalyst is a substance which can change the rate of reaction.
Characteristics of catalyst:
1. Chemically, the catalyst remains unchanged during a reaction.
2. Catalyst does not change the quantity of the product.
3. Catalyst is specific, which means different chemical reaction may have
different catalyst.
4. Just a small amount needed to achieve a big increase in the rate of
reaction.
5. More amount of catalyst used can further increase the rate of reaction.
6. Catalyst in powder form can further increase the rate of reaction.
7. Catalyst may undergo physical change in a reaction.
30. COLLISION THEORY
The particles of the reacting
need to touch to enable the
formation or breaking of the
bonds for a reaction to happen.
Collisions of particles of a
reacting substance need to
achieve certain minimum energy
(Activation Energy) in order to
produce a reaction.
Particles that collide also need
to have the correct orientation
of collision.
31. 3.1 ACTIVATION THEORY
The activation energy is the
minimum energy that the
particles of the reactants must
achieve at the time of collision
in order for a chemical reaction
to take place.
The value of the activation
energy is different for different
reactions.
A reaction with high activation
energy occurs slowly
whereas a reaction with low
activation energy occurs fast.
32. 3.2 EFFECTIVE COLLISION
Effective collision is
the collision that
produces a reaction
achieving minimum
energy that is
sufficient and with
the correct
orientation of
collision.
33. 3.3 ENERGY PROFILE DIAGRAM
In the diagram of the energy
profile, the activation energy
is shown by the difference
in energy between the peak
of the graph and the level of
the energy of the reacting
substance
34. 3.4 EXPLAINATION BY COLLISION THEORY
1. Size of Reactants
When the size of the solid substance that reacts is smaller,
its total surface area exposed becomes larger.
collisions frequency between the reactants increases.
frequency of effective collisions also increases
increases the rate of reaction
35. EXPLAINATION BY COLLISION THEORY
2. Concentration
When concentration of reactant increases ( )
Number of particle per unit volume increases
Frequency of collision between particles increases
Frequency of effective collision between particles increases
Rate of reaction increases
36. EXPLAINATION BY COLLISION THEORY
3. Temperature
When the temperature of a
reaction increases,
the particles of the reacting
substances move faster.
collisions frequency between the
reactants increases.
frequency of effective collisions
also increases
increases the rate of reaction.
37. EXPLAINATION BY COLLISION THEORY
4. Presence of catalyst
When a positive catalyst is used
in a reaction,
the catalyst provide an
alternative path by lowering
activation energy for the
reaction.
frequency of effective
collisions increases
increases the rate of
reaction.
38. EXPLAINATION BY COLLISION THEORY
5. Pressure of Gas
When pressure of a gas increases ( )
Number of particles per unit volume
increases
Frequency of collisions between
particles increases
Frequency of effective collision
between particles increases
The rate of reaction increases
40. ASSIGNMENT 1
Find information related to the examples application of the factors that affect the
rate of reactions:
1. The size factor
2. Concentration factor
3. Temperature factor
4. Catalyst factor
Based on the information collected, prepare a slide presentation.
Find at least 2 examples per factor.
Each person will be given 10-20 minutes per session
Submission of slide presentation will be on 1.03.2023
Attached the slide presentation in google classroom in PPT format.
