CSEC Rates of Reaction 2014.pptx

8/9/2019 CSEC Rates of Reaction 2014.pptx

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RATES OF REACTION

CSEC Chemistry

Prepared by M. J. McNeil, MPhil.

Departmet !" C!ti#i$ %Ed#cati!& St#dies

P!rtm!re C!mm#ity C!lle$e

Mai Camp#s

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'ECT(RE O)JECTI*ES I

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+AT DOES TE

RATE OF A REACTION MEAN-

What is the rate of these reactions?

Chemical reactions require varying le$ths !" time

for completion.

The speed of different chemical reactions varies

h#$ely.

Some reactions are ery "ast and others are ery

sl!/.

Reaction rate is the rate or speed at which pr!d#cts

are "!rmed or reactats are c!s#med.

A reacti! rate depends on the characteristics !" the

reactats ad pr!d#cts and the c!diti!s under

which the reaction is run.

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slow fast very fast


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This is the area of chemistry concerned with the speeds, or rates, at which a

chemical reaction occurs and the path ta0e y the reaction.

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CEMICA' 1INETICS


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A B

time


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+2 ST(D2 REACTION RATES-

!y understanding how the rate !" a reacti! is affected y cha$i$

c!diti!s, one can learn the details of what is happening at the m!lec#larleel.

The length of time it ta"es to ba0e ch!c!late chip c!!0ies depends on the

rate at which ba0i$ s!da #s!di#m bicarb!ate or hydr!$e carb!ate$

decomposes at %&& oC.

'anufacture of Ammonia %aber Pr!cess& 3 specific conditions

#temperat#re ad press#re$ to aid the reaction to proceed in a c!mmercially

"easible length of time.

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MEAS(RIN4 RATES OF REACTION

Rate !" reacti! is a meas#red cha$ed in the am!#t !" a speci"ic reactat

!r pr!d#ct as a function of time.

Rate ( meas#red cha$e in a $ie pr!perty

time ta0e for change to occur

)uring any chemical reaction, it has een found that the c!cetrati! of reactats

decreases at the same rate as the c!cetrati! !" the pr!d#ct icreases. *owever,

the change in concentration per unit time is sometimes challenging to measure directly.

+ther property changes which are often used are

%i& !l#me !" a $ase!#s pr!d#ct

%ii& c!l!#r itesity

%iii& am!#t !" a precipitate "!rmed

%i& decrease i mass %i" $as is liberated& 7

Measuring the rate of a reaction means measuring the change in the amount of a reactant or


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+2 ARE SOME REACTIONS

FASTER TAN OTERS-

Some people can r# "ast, others

r# m!re sl!/ly, and still others

d! !t r# at all. 'olecules are

the same- some are ery reactie,

others react less rapidly, and still

others react ery sl#$$ishly.

The CO''ISION TEOR2

eplains this.

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CO''ISION TEOR2 OF REACTION

/n order for a chemical reaction to occur, the

following TREE c!diti!s M(ST e

met

#i$ The particles of the reacti$

s#bstaces must c!llide with each other

to brea0 !ld b!ds in the reactats, and

"!rm e/ b!ds in the pr!d#cts.

The more c!llisi!s in a system, the

more li"ely c!mbiati! of molecules

will happen.

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/n order to react the following conditions must

e met

#ii$ The colliding particles must produced

s#""iciet eer$y to brea0 the !ld b!ds in

the reactats. This energy is termed the

actiati! eer$y5, #to e discussed in

details later$.

N!t all c!llisi!s produce the required

energy, therefore !t all c!llisi!s results in

a reacti! !cc#rri$.

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/n order to react the following conditions

must e met

#iii$ Reactant particles m#st c!llide with

the c!rrect !rietati! so that the

energy produced y the collision can

e passed on to the onds to e ro"en.

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FACTORS TAT AFFECT

REACTION RATES

Through etensive e6perimets, chemists have determined that the rate of a

reaction depends on si6 variales

C!cetrati! !" reactats

Temperat#re

Catalyst S#r"ace Area %Particle Si7e&

Press#re

'i$ht

'ET8S 'OO1 AT TEM IN DETAI'.

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EFFECT OF CONCENTRATION ON

TE RATE OF A REACTION

'ore often than not, the rate of a reaction

icreases when the c!cetrati! of a reactant

is icreased and ice3ersa.

Why increasing the concentration increases the

rate of reaction and vice0versa?

At a hi$her c!cetrati!, there are m!re

particles in the same am!#t of space. Thismeans that the particles are more li"ely to

react.

*ence, increasing the p!p#lati! of reactants

increases the li"elihood of a s#ccess"#l

c!llisi!. The converse of this statement is also

true.

/n some reactions, however, the rate is

#a""ected y the concentration of a

particular reactant, as long as it is

present at some concentration.

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highlower concentration

IN*ESTI4ATION OF TE EFFECT OF


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IN*ESTI4ATION OF TE EFFECT OF

CONCENTRATION ON REACTION RATE

Add the Cl to the Na9S9O: in the flas".

Record the time ta0e for the ; to disappear.

Repeat with di""eret c!cetrati!s of Na9S9O:

The ierse the time #


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The formation of a pale yell!/ %c!ll!idal& precipitate !" s#lph#r can e used to monitor the progress of the reaction.

1lease visit http://www.youtube.com/watch?v=r4IZDp!"b# to view this expt. (7 mins

The rate !" a chemical reacti! is NOT affected y a cha$e i !l#me of the reacting solut

provided that the c!cetrati! remains the same.

HCl Na2S2O3 H2O+NaCl

IN*ESTI4ATIN4 TE EFFECT OF

CONCENTRATION ON RATE

+ ++ SO2

1%

http://www.youtube.com/watch?v=r4IZDPpN-bkhttp://www.youtube.com/watch?v=r4IZDPpN-bkhttp://www.youtube.com/watch?v=r4IZDPpN-bkhttp://www.youtube.com/watch?v=r4IZDPpN-bkhttp://www.youtube.com/watch?v=r4IZDPpN-bk


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CONCENTRATION ON RATE

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TE EFFECT OF CONCENTRATION ON RATE

R

A

T

E

CONCENTRATION

Conclusion

?

Rate is directly

proportional to

concentration

1

Time

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SETTIN4 (P TE RATES E;PERIMENT

What e>#ipmet is needed to iesti$ate the rate !" hydr!$e e!led?

gas syringe

ruer ung

ruer connecter glass tue

conical

flas!

magnesium

hydrochloric

acid

DETERMININ4 REACTION


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h y d

r o g e n p r o d u c e d

( c m 3 )

time (seconds)10 20 30 40 50

10

20

30

40

50

60

70

00

"

y

DETERMININ4 REACTION

RATES FROM 4RAPS

rate of reaction

"

y

rate of reaction (

45 s

67 cm2 rate of reaction ( 9.9? cm:=s

The gradient of the graph is equal to the initial rate of reaction

at that time.


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EFFECT OF TEMPERAT(RE ON RATE

The hi$her the temperat#re, the "aster the

rate !" a reacti! and ice3ersa.

/n many chemical reactions, a rise in

temperature of


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TEMEPAT(RE )ATTERIES

Why are batteries more li"ely to r#d!/ m!re >#ic0ly in c!ld /eather?

At l!/ temperat#res the

reaction that generates the

electric current proceeds m!re

sl!/ly than at hi$her

temperat#res.

This means atteries are less

li"ely to deliver enough

c#rret to meet demand.

O+ DOES TEMEPERAT(RE AFFECT RATE-


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O+ DOES TEMEPERAT(RE AFFECT RATE-

The reacti! etween s!di#m thi!s#l"ate and hydr!chl!ric

acid produces s#l"#r.

S#l"#r is s!lid and so it turns the s!l#ti! cl!#dy.

*ow can this fact e used to meas#re the e""ect !"

temperat#re on rate !" reacti!?

hydrochloric

acid

sodium

chloridesulfur

sodium

thiosulfate + +sulfur

dio"ide ++

Na#$#O%(a!)

#&Cl

(a!)

#NaCl

(a!)

$

(s)++ $O#(g)

+ +



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TEMPERAT(RE ON RATE

Add the Cl to the Na9S9O: in the flas".

Record the time ta0e for the ; to disappear.

Record the temperat#re after mi6i$.

The ierse the time %


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"e#t

REPEAT AT DIFFERENT TEMPERAT(RES

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R

A

T

E

TEMPERATURE

Conclusion ?

Rate increases

with increasingtemperature

1 Time

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EFFECT OF CATA'2ST ON RATE

A catalyst is a s#bstace that

icreases the rate !" a reacti!

/ith!#t bei$ c!s#med i the

!erall reacti!.

The catalyst generally d!es !t

appear in the !erall balacedchemical e>#ati! #although its

presence may e indicated y

writing its formula over the arrow$.

The presence of a s!lid catalyst #finely divided$ provides a s#r"ace area over

which gas molecules react #c!tact catalyst$, resulting in m!re c!llisi!s and

hence icrease the reacti! rate.

The gases must e dried #CaO$ and purified efore passing them over thecatalyst to prevent 8p!is!i$9 of the catalyst.

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Catalysts NE*ER produce more product 0 they :ust produce the same amount more quic"ly.


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Ay reacti! ! a s!lid ca !ly ta0e place

! the s#r"ace !" the s!lid.

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EFFECT OF CONCENTRATION


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EFFECT OF CONCENTRATION

OF A CATA'2ST ON RATE

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Di""eret catalysts /

di""eret /ays, b#t

reacti!8s actiati!

&$%9&l%9

&a>%,)r

&a>%99 OO,9O,9

Catalysts NE*ER produce more product 0 they :ust produce the same amount more quic"ly.

5T/! mai "#cti!s of a catalyst

$ A catalyst speeds up reactions y

red#ci$ the Bactiati!

eer$y needed for successfulreaction.

$ A catalyst may also provide an

alteratie mechaism, or

path/ay, that results in a faster

rate.

A catalyst is a substance that increases the rate o


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A catalyst is a substance that increases the rate o

chemical reaction without itself being consumed.

ratecataly%ed & rateuncataly%ed

E*ER2DA2 CATA'2ST


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E*ER2DA2 CATA'2ST

Nic0el is a catalyst in the production of margarine

#hydrogenation of vegetale oils$.

'any catalysts are trasiti! metals or their compounds.

;or eample

Plati#m is a catalyst in the catalytic

c!erters of car e6ha#sts. /t cataly


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EFFECT OF S(RFACE AREA

%PARTIC'E SIE& ON RATE

!ecause the reaction occurs at the s#r"ace ofthe s!lid reactat or catalyst, the rate

icreases with icreasi$ s#r"ace area

#state !" s#b3diisi!$ of the solid and ice3

ersa.

*ence, the reacti! is directly pr!p!rti!al

to the s#r"ace area of s!lid reactat.

/n such a reaction, c!llisi! occurs etween

the m!i$ particles and the s!lid reactat,

hence the larger the surface area, the greater

the opportunities for collisions and the

greater the rate of reaction.

The c!erse of this condition is

also tr#e.

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EFFECT OF SURFACE AREA ON


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EFFECT OF SURFACE AREA ON

RATE

3%

Repeat using the sam

p!/dered CaCO:

and the same !l#m

and the same c!ce

Rec!rd the time ta0e "!r

CO9 t! ed

% N! "#rther ma


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RESULTS

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The rate !" release !" CO9 $as can e used to

monitor the pr!$ress of the reaction.

1lease visit http://

www youtube com/watch?v=&'tw#um )*

HCl CaCO3 H2O +


PARTIC'E SIE ON RATE

+ + CCaCl2

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Add the Cl t! a lar$e chips !" CaCO i the "las0

http://www.youtube.com/watch?v=FJtwkum_QAYhttp://www.youtube.com/watch?v=FJtwkum_QAYhttp://www.youtube.com/watch?v=FJtwkum_QAYhttp://www.youtube.com/watch?v=FJtwkum_QAYhttp://www.youtube.com/watch?v=FJtwkum_QAYhttp://www.youtube.com/watch?v=FJtwkum_QAY


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Add the Cl t! a lar$e chips !" CaCO: i the "las0

As C+4 is released the mass of the flas" drops

"e

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Res#lt

Fiely diided particles react "aster tha lar$e particle40


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EFFECT OF PRESS(RE ON RATE

Why does icreasi$ the press#re on$ase!#s reactats icrease the rate of

reaction and ice3ersa?

As press#re icreases, the space in

which the particles are moving

ecomes smaller.

The gas particles bec!me cl!ser

together, icreasi$ the "re>#ecy of

c!llisi!s. This means that the particles

are more li"ely to react.

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lower 'ressure h


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EFFECT OF 'I4T ON RATE

'i$ht eer$y of a s#""icietly high frequency can brea0 some chemical b!ds and sospeed #p chemical reaction.

=amples of li$ht sesitie reactions are

Reactions of hydr!$e with hal!$es.

#i$ *4 > Cl4 4*Cl #e6pl!sie$. This reaction is slow and fast in diffused and

direct sunlight$.

#ii$ 1hotosynthesis construct the equation for this reaction.

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4'OSSAR2


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actiati! eer$y 3 The amount of energy needed to start a

reaction #for ond rea"ing to occur$.

catalyst 3 A sustance that increases the rate of a chemical

reaction without eing used up.

c!cetrati! 3 The numer of molecules of a sustance in agiven volume.

rate !" reacti! 3 The change in the concentration over a

certain period of time.


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4%


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THE END


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THE END

NOT SO QUICK!

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JUNE 2013, Q4

%0


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%1


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%2

JUNE 2012 Q1


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JUNE 2012, Q1

%3


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%4


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%%


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%6


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%7


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JANUARY 2009 Q1


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JANUARY 2009, Q1

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6%


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JUNE 2007, Q5


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J , Q

68


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JUNE 2005, Q1


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, Q

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JUNE 2004, Q1


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7%


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Documents

CSEC Rates of Reaction 2014.pptx