chemistry form 5 chapter 1 - rate of reaction

7/28/2019 Chemistry Form 5 Chapter 1 - rate of reaction

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Rates Of Reaction

Flow Of Learning


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Meaning Of Rate Of Reaction

MEASUREMENT OF RATES OF REACTION:

Plot graph of quantity of product /

reactant against time

Calculate the average rate of reaction

Calculate the rate of reaction at the

specific time from the graph.

EXPLANATION FOR THE RATE OF REACTION BASED ON COLLISIONTHEORY :

Particle Size

Concentration

Temperature

Catalyst

-The meaning ofCollision Theory.

-To explain how each factor increases


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Is proven by

Experiment On Effect OfSurface Area

Experiment On Effect OfConcentrationExperiment On Effect OfTemperature

Experiment On Effect OfCatalyst


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Application of The Rate Of reaction In

daily Activities


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Rate Of Reaction

Observable changes

in quantity that use

to determine rate of

reaction

Meaning rate of

reactionUnit for rate of

reaction

Measurement

Rate Of Reaction

Avarage rate of

reaction

Rate Of reaction at

specific time

Factors that affect rate of reaction


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Speed= Speed=

=

= 300km/h

=

= 100km/h

i


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Chemical

Reaction Types

Bonds are made / brokenChange in oxidation statesPlasma

P+1 P+1

2

1

Li+1


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Chemical properties/

changes/ reactions(i.e., reactivity,

combustibility).

development of a gas,formation of precipitate

and change in color).

Reactivity

Combustibility

Gas formation

Precipitate

Color change


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Hydrogen-VERY reactive.

Helium-Non-reactive.


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The speeds of reactions are very variedRusting is a slow reaction, you hardly see

any change looking at it!The weathering of rocks is an extremely very

slow reaction.

weathering of rocks


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The fermentation

of sugar to alcohol

is quite slow butyou can see the

carbon dioxide

bubbles forming in

the 'froth' in alaboratory

experiment or beer

making in industry!

Bubble gas


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A faster reaction example is

magnesium reacting with

hydrochloric acid to form

magnesium chloride and hydrogen

or the even faster reaction between

sodium and water to form sodium

hydroxide.

Combustion reactions e.g. when afuel burns in air or oxygen, is a very

fast reaction.


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Combustibility

The tendency toreact with

Oxygen,

releasing heat.

O2

BURNING

d f h l h


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evidence of Chemical Change:

development of a gas

formation ofprecipitatechange in color


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Meaning Of Rate Of Reactions

The rate of reaction is a measurement of the

change in the quantity of reactant or product

against time:

Rate Of Reaction= Change in quantity of reactant / product

Time taken

Student ans: Changes of reactant or product

against time (0 Mark)


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Meaning Of Rate Of Reaction

A rate of reaction is high if the reaction occurs

fast within a short period of time..

A rate of reaction is low if the reaction occurs

slowly within a long period of time..

A rate of reaction is inversely proportional to

time:

Rate of reaction 1

time taken


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Meaning Of Rate Of Reactions

The Higher rate ofreaction the shorter

time taken to

complete thereaction

The lower rate of

reaction the longertime taken to

complete reaction

granule powder

5 minute 1 minuteWhich is the higher rate ofreaction?


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CaCO3 (s) + 2HCl (aq) CaCl2 (aq) + H2O + CO2 (g)

Observable Changes Measurement Of Reaction

Changes of mass Rate of reaction =

= Z gs-


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Observable

Changes

Measurement Of Reaction

Changes of

volume

Rate of reaction =

= Z cm3s-


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The change in amount of reactant / product that can

be measured :

Decrease in total quantity of mass / concentration of

the reactant per unit of time.

Increase in total amount of mass / concentration ofthe product of reaction per unit of time

Total volume of the gas released.

Formation of precipitate.

Observable changes


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Decrease in total quantity of mass /

concentration of the reactant per

unit of time.


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Increase in total amount of mass /

concentration of the product of

reaction per unit of time


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Total volume of the gas released.


waterburette

Deliverytube

Conical flask

Must

shade!


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Formation of precipitate.

Na2SO3+2HClNaCl+S+SO2+H20PERCIPITATE

stopwatch


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Precipitate theformation of insoluble

ionic compounds.

Does NOT dissolve in water.
http://icn2.umeche.maine.edu/newnav/newnavigator/images/P7280069.JPG


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Example:

Study the reaction: Between calcium carbonateand excess 1 mol dm-3 hydrochloride acid.


Mass of CaCO3

(g)

time (s)

Concentration of HCl(mole dm-3)

time (s)


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Concentration of CaCl2(mole dm

-3)

time (s)

Volume of CO2

(cm3)

time (s)


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Observable changes

stopwatch


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Observable changes

Hydrometer


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Observable changes

Hydrometer


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Observable changes

Displacement Of water


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Remember !!!

Quantities ofreactant

will decreases against

time

Quantities ofproduct

will increases against

time



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Measurement Rate Of Reaction

Two ways to measure rate of reaction.1. Average Rate Of Reaction. :

It is determined by calculating the total amount of

reactant used or the total amount of product

formed in a specific time.

2. Rate Of Reaction at a specific time :

It is determined by calculating the gradient of the

graph at the time.


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Introduction to the Rate of Reaction

1. A reaction between small pieces of excesscalcium carbonate with 80 cm3 hydrochloric acid

0.05M is conducted a laboratory to study the rate

of reaction at interval time. The volume of gas

released is recorded in the table below.

Time (seconds) 0 30 60 90 120 150 180 210 240Burette reading (cm3) 49.5 33.5 23.5 16.0 10.5 5.0 2.0 2.0 2.0


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40

30

40

30

37.00cm3 27.00cm3

Volume : 37-27=10 cm3


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(a)

Draw an apparatus to shows how this experimentcan be conducted at laboratory.

Must label the diagram!


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x

x


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(b)

Write a balance chemical equation for thisreaction.



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(c)CaCO

3

+ 2HCl CaCl2

+ H2

O + CO2

CaCO3 + 2H++2Cl- Ca2++2Cl- + H2O + CO2

CaCO3 + 2H+

+ Ca2+

+ H2O + CO2

Remember !!!

Only separatesoluble

salt

Dont separate covalent and

insoluble salt


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(d)

Carbon dioxide gas


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(e)A reaction between small pieces of excess calcium carbonate

with 80 cm3hydrochloric acid 0.05M is conducted alaboratory to study the rate of reaction at interval time.

Number of mole in the solution will use :

Mol, n

=

MV

1000

0.05(80)

1000

=

= 0.004 mol


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(f)CaCO

3+ 2HCl CaCl

2+ H

2O + CO

2

From the chemical equation :

Mole Ratios:

2 mol HCl : 1 mol CO2

0.004 mol HCl : 0.004 mol HCl

2 mol HCl

1 mol CO2

= 0.002 mol CO2

Volume of gas Co2 at

room condition

= 0.00224

0.048 dm3

=


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(g)

Because some of carbon dioxide gas can

escape to surrounding during the

experiment.


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(h)Time (seconds) 0 30 60 90 120 150 180 210 240

Burette reading (cm3) 49.5 33.5 23.5 16.0 10.5 5.0 2.0 2.0 2.0Volume CO2 (cm

3) 0 16 26 33.5 39 44.5 47.5 47.5 47.5

Time(second) 0 30 60 90 120

Burette

reading(cm3)

x

49.5

y

33.5

z

23.5

Total volume

of gas(cm3)

x-x

0.00

x-y

16.00

x-z

26.00

Volume of CO cm3


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0

5

10

15

20

25

30

35

40

45

50

0 30 60 90 120 150 180 210 240 270

Volume of CO2, cm

Time , s

Connect thepoint without

using ruler!

Not all the point

is connected

Volume of CO cm3


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0

5

10

15

20

25

30

35

40

45

50

0 30 60 90 120 150 180 210 240 270

Volume of CO2 cm

Time s

Cannot like this graphStraight line

Its must be

smooth graph

(i)


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Average Rate Of reaction

The average rate of reaction in the first 90 seconds.

= The total volume of gas released in the first 90 seconds

Time taken

(i)

Time (seconds) 0 30 60 90 120 150 180 210 240

Burette reading (cm3) 49.5 33.5 23.5 16.0 10.5 5.0 2.0 2.0 2.0

Volume CO2 (cm3) 0 16 26 33.5 39 44.5 47.5 47.5 47.5

= 33.590=0.372 cm3s-1

Not cm3 per second

unit


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i(ii)

Time (seconds) 0 30 60 90 120 150 180 210 240Burette reading (cm3) 49.5 33.5 23.5 16.0 10.5 5.0 2.0 2.0 2.0

Volume CO2 (cm3) 0 16 26 33.5 39 44.5 47.5 47.5 47.5

47.5180= 0.264 cm3s-1

The average rate of reaction in the whole experiment.

= The total volume of gas released in the whole experiment

Time taken

=


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Tangent

Only touch 1 point of curve

Cannot touch more

than 2 point because

each of point have

different gradient


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0

5

10

15

20

25

30

35

40

45

50

0 30 60 90 120 150 180 210 240 270

Same length

Same angle degree

A l i f d t


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Total Volume of CO2(cm3)

Time (second)

Analysis of data

A

B

C

D

E

F

t1 t3t2

Rate of reaction at t1 = gradient AB

Rate of reaction at t2 = gradient CD

Rate of reaction at t3 = gradient EF

Each of point have

different gradient!


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(k)

Explain why does there is a difference of the rateof reaction at 30 second and 120 second.

Ans: Rate of reaction at 30 second ishigher because number of particles of

reactant is higher than 120 second


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chemistry form 5 chapter 1 - rate of reaction

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