exp1_mangkuk

7/18/2019 exp1_mangkuk

http://slidepdf.com/reader/full/exp1mangkuk 1/10

Laboratory Report

CAB 1023 Physical Chemistry

Name : Kamesh V’shn Nair !" :

200#0

Name : !" :

$%periment 1: Reaction Rate an& Acti'ation $ner(y o) Aci& hy&rolysis o) $thyl

Acetate



CAB 1023 Physical Chemistry

Laboratory Report *heet

$%periment 1 : Reaction Rate and Activation Energy of the Hydrolysis of Ethyl Acetate

+b,ecti'e

1. To determine the rate constant for the acid hydrolysis of ethyl acetate at three (for

more) temperatures.2. To calculate the activation energy of the reaction from the measured rate constants.

Proce&re

1. Apparatus assembled according to figure 1.2. The solutions reuired for the e!periments are prepared as follo"s#

A.$.1 molar hcl solution in a volumetric flas% by diluting 2&ml of 1.$ m

hcl to 2&$ ml "ith distilled "ater.

'.$.2 molar naoh solution in a volumetric flas% by diluting 2$ml of 1.$ m

naoh to 1$$ml "ith distilled "ater.

. 1$$ml of $.1m hydrochloric acid is poured into an erlenmeyer flas%"hich can be

sealed "ith stopperand temperature eulibrate it for appro!imately 1& minutes in

a temperature controlled bath at t*+$%(the e!act temperature),. At t-$reaction started by adding & ml of ethyl acetate room temperature and

sha%e the solution briefly.&. ut the solution in the temperature/controlled bath and let it eulibrate for 1$

minutes.0. An erlenmeyer flas% (2&$ml) is filled "ith 1$$ml of cold "ater.. ill the buret "ith $.2m hydro!ide solution.3. After reaction mi!ture has euilibrated for about 1$ minutesta%e &ml sample and

pour it into the erlenmeyer flas%(2&$ml)containing the cold "ater. This "ill stop

the reaction and the mi!ture should be titrated immediately.4. Add fe" drops of phenolftalein to the reaction mi!ture and titrate the solution

against $.2m of sodium hydro!ide solution.1$. Repeat steps 0 through 4 for a total time period of &$ minutes and sampling

intervals of 1$minutes.11. Terminate this measurement series after &$ minutesand save the euilibrated

reaction mi!ture for determination of vnaoh ,12. 5etermination of v naoh

a. Remove reaction mi!ture from the "ater bath and place it in another "ater

bath at temperature $6c for 2$ minutes.



b. 7btain & ml sample and place it in the erlenmeyer flas% (2&$ml) containing

1$$ml of cold "ater. Titrate this mi!ture against $.2m naoh solution.1. 5etermination of v naoh$

a. Add & ml of $.1 m hcl into an erlenmeyer flas% and place it in the "ater bath

(at temperature of t1) for 1& minutes.

b. Add 1$$ ml of cold "ater to the flas% and titrate against $.2 m naoh. Thevolume of naoh must be corrected for the ester portion "hich is absent

hereby a factor of 1$$81$&.1,. Repeat e!periment at temperature of 13% and ,% if time permits.

Laboratory Report *heet

1- .y&rolysis o) ethyl acetate at 303K

a. 5etermination of 9 :a7H;

9 :a7H; - 0. m<

b. 5etermination of 9 :a7H$

9 :a7H from the titration - 2. m<

9 :a7H$- (9 :a7H)(1$$81$&) - 2.& m<

tmin 9 :a7Htm< =-(9 :a7H;/9 :a7H$)/(9 :a7H;/ 9 :a7Ht)

ln =

$ 9 :a7H$ - 2.& 1.$$$ $.$$$

1$ .$ 1.12& $.11,

2$ .& 1.241 $.2&&$ .3 1.,2, $.&

,$ ,.$ 1.&$ $.,2&

&$ ,. 2.$0& $.2&

; 9 :a7H; - 0. undefined undefined


a. 5etermination of 9 :a7H;9 :a7H; - 12.2 m<

b. 5etermination of 9 :a7H$9 :a7H from the titration - .$ m<

9 :a7H$- (9 :a7H)(1$$81$&) - 2.30 m<



tmin 9 :a7Htm< =-(9 :a7H;/9 :a7H$)8(9 :a7H;/ 9 :a7Ht)

ln =

$ 9 :a7H$ - 2.30 1.$$$ $.$$$

1$ .$ 1.1$& $.$1&

2$ . 1.$, $.$1,

$ ,.2 1.1,$ $.11,$ ,.3 1.103 $.1&&

&$ &., 1.24 $.20$

; 9 :a7H ; - 0. undefined undefined


a. 5etermination of 9 :a7H;9 :a7H; - .2 m<

b. 5etermination of 9 :a7H$

9 :a7H from the titration - 2. m<

9 :a7H$- (9 :a7H)(1$$81$&) - 2.& m<

t.min 9 :a7Htm< =-(9 :a7H;/9 :a7H$)8(9 :a7H;/ 9 :a7Ht)

ln =

$ 9 :a7H$ - 2.0 1.$$$ $.$$$

1$ .$ 1.121 $.11,

2$ . 1.2 $.2$4

$ ,.2 1.02 $.&00,$ ,.3 2.,0 $.4$

&$ &., ,.111 1.1,

; 9 :a7H; - 0. undefined undefined

- 5etermine the rate constants %> from the (ln = vs t ) plots for the hydrolysis

reactions at $ ? 13 ? and , ?.



%>$ - %>13 - %>, -

- $.$2, - - $.$12

#- Determine the slope of the (ln k’ vs ) plot.

ln k’ -3.730 -5.435 -4.40

m -

- 1.03$

- Calculate the activation energ! "a for the h#rolsis of ethl acetate

ester.

$

$ 3%.7 k&

- 'f the h#rolsis reaction is carrie# out at other temperature range! hat

ill the value e for the activation energ*

/ +he activation energ #oesn’t change ith temperature.

- ,hat ill e the value of the activation energ if catalst is use# for the

h#rolsis process*

/ ctivation energ ill #ecrease.



@raph ln = vs T





"iscssion

E!plaination about the observation#

or every three different temperatursas the temperature increasesthe higher

volume of sodium hydro!ide is reuired to titrate the acid hydrolysis of ethylacetate. The initial volume of sodium hydro!ide for the $? e!periment is 2.&ml.

The initial volume of sodium hydro!ide for the 13? is 2.0ml. Thenfor the , ?

e!perimentthe initial volume of sodium hydro!ide reuired "as 2.0ml. As "e observed"hen "e titrated the solution consists of acid hydrolysis for ethyl

acetate that has been added "ith phenolftaleintitrated "ith the sodium hydro!ide

solution in the buretthe reaction mi!ture sho"ed the colour changefrom colourlessto pin% .

Effectiveness of the e!periment#

hen the &ml sample of reaction mi!ture is suc%ed through the pipetteand to be

transferred into the Erlenmeyer flas% containing the cold "aterthe sample must be

transferred fully and accurately. The &ml sample is to be eliminated from the pipette

into the Erlenmeyer flas% by the end part of the pipettetouching the "all surface of

the Erlenmeyer flas%so that the &ml sample can be transferred totally. The titration must be done immediatelyafter the &ml sample of reaction mi!ture is

obtained to get the accurate result and to monitor the colour change. 'esidesthe eye level ta%ing the measurement of the volume of chemicals so "e get

the e!act volume of chemicals as mentioned in the manual lab.

The buret must be "ashed "ith sodium hydro!ide to eliminate any e!cessive

chemical molecules from the previous e!periment. 'esidesma%e sure that all the apparatus are really clean and dry to ensure that "e

obtain the accurate result for the e!periment. lusthis is also the step to prevent any

impurities in the apparatus from affecting the e!periment result.

Bomment on apparatus or method used and suggestion to improve it#

+he apparatus that are use# are suppose# to e han#le# carefull!as

some of them might e fragile!an# coul# have roken. 'nstea# of takingother groups apparatus!on apparatus that are provi#e# shoul# e

taken care an# prevente# from reaking an part of them. Concentrate# solution such as so#ium h#roi#e /.0 an# h#rochloric

/.0 shoul# e han#le# ver carefull!as the nee# to e #ilute#. +ransferring those solutions into respective erlenmeer 1asks shoul# ema#e using the funnel!as this step oul# make all the contents arefull transfere# into those 1asks.

2urthermore!the erlenmeer 1ask containing ethl acetate ith the

#ilute# h#rochloric aci# hen put in the ater ath!it shoul# emaintaine# in the ath. 't shoul# not e taken out from the ath!as this



oul# aect the temperature!hile it eing reuire# to e titrate#against the so#ium h#roi#e #ilute# solution from the uret.

Ctatement about science facts and theories learned from the result of the e!periment#

The rate constant is related to the temperature by the e!pression

<n %>- (/Ea8RT) D ln A

in hich k is the rate constant !"a is the energ of activation! is the

gas constant an# t is asolute temperature.

The larger the energy of activation the greater the change of % "ith temperature.

rom e!periment "e can calculate the rate constant% by finding the slope graph of

ln = vs T. hile the activation energy can alternatively be determined from theslope of the linear relation bet""en ln %> and 18T according to the euation above.

rom the result of e!periment that "e getgraph of ln = vs T "ill be linear mean to

say ln = is proportional to T. f ln= increase hence T "ill also be increase.

Analysis of error(accuracy and precision)#

+here are errors that occur #uring the eperiment is carrie# out.

6aralla error - the ees are not parallel ith the meniscus level of the

urette hen rea#ing the measurements. ero error 8 the rea#ing an# level marke# on the urette an# pipette is

not clear that lea#s to 9ero error. ,rong value of :a;< use# to neutrali9e <Cl #ue to errors hen #oing

the titration. +he titration is not stoppe# imme#iatel hen theneutrali9ation point is reache# an# lea#s to more :a;< a##e# to the

<Cl solution. lthough the activation energ value from the graph ln k versus /=+ is

not accuratel euals the value of the one calculate# efore(using rate

constant)!e manage# to get the precise# #ata for the activation

energ value. +his happens to e as the value is >ust a slight #ierence

from one another!comparing the value otaine# from the slope (ln k vs

/=+) an# value calculate# efore(using rate constant!ln ? vs +).

roblems faced#

e have difficulties "hen "e tried to start the e!periment. e did not understandstep , and & in lab manual in method section but after demonstrator sho"ed the

mechanism of the e!periment on the "hite board and "ith some e!planation from him

"e are totally understood for the right steps to conduct this e!periment.



hile "e "ere doing the e!perimentthe funnel accidentally bro%en.. t is hard

for us to pour sodium hydro!ide into the buret. e have to borro" funnel from other

groups.

7n the last part of e!periment"hich "e have to find 9 :a7H at infinity "e had

made mista%e. e forgot to put phenolphtalein in hydrochrloric acid "ith ethyl acetatesolution. As result of the mista%e"e have to repeat the last part to get the e!act volume

of sodium hydro!ide that react "ith hydrochrcloric acid.

Conclsion:

2rom the eperiment!e otaine# the rate constant that e got for

303 @ is 0.0A4 !for 3/B @ is an# for 343 @ is 0.0/A.ase# on

the results from the graph! the activation energ that e get is 3%.7

k&=mol. +he slope from the graph ln ? vs t(min) #etermine# the rate

constant for each temperature for the h#rolsis of ethl acetate.+heslope from the graph ln k’ vs /=+ #etermine# the activation energ foroverall process that e can see #iers from the eperimentalcalculation.

Re)erences:

aorator anual of 6hsical Chemistr Eecon# "#ition!&ohn ,ilean# Eons!<oraceD.Crockfor#! <.,allace air#! &ohn ,. :oell! 2orrest,. Fet9en

6hsical Chemistr! Davi# ,.all page 5B-%0!%%-B%

ecture notes 6hsical Chemistr

ChemistrG +he Central Ecience! +heo#ere ! ron!<. "ugene emaan# ruce ".ursten! /0th "#ition!6earson(6rentice <all)

Documents

exp1_mangkuk