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Transcript of Rate of reaction between sodium thiosulphate COURSWORK CHEMISTRY .I..docx
7/23/2019 Rate of reaction between sodium thiosulphate COURSWORK CHEMISTRY .I..docx
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Stephano Pina
Rate of reaction between sodium thiosulphate
and hydrochloric acid investigation
Contents:
Aim………………………………………………. 2
Chemical ideas ………………………………………………. 2-7
Ris assessment……………………………………………….!
"ethods……………………………………………….#
"aing the standard solution……………………………………………….#
$%periment &……………………………………………….&'-&2
$%periment 2……………………………………………….&(-&)
$%periment (……………………………………………….&*-&!
$%periment+……………………………………………….&!-2'
$%periment )……………………………………………….2'-22
Conclusion……………………………………………….2(
$valuation……………………………………………….2+-27
References……………………………………………….2!
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Aim:
In this investigation I aim to fnd out the rate o reaction between
sodium thiosulphate and hydrochloric acid and the eect o dierentvariables on it. The reaction consists on the ormation o sulphur as a
precipitate and the rate depends on the time taen or it to orm. I will
use a dierent range o methods and techni!ues to show the
in"uence o some variables on the rate o reaction. I will investigate
the concentration# temperature# catalysts and other acids aect on
the rate reaction. In order to achieve that or the concentration I will
alter concentration o both reactants by diluting them and use the
graphs to determine the order with respect to each reactant# and rom
this I hope to write the rate e!uation and conclude who manymolecules o each reactant are in the rate determining step. $or the
temperature I am hoping to try the e%periment at dierent
temperatures by using water baths and woring out i the rate
increase or decrease with the increase in temperature. $rom this data
I e%pect to plot a graph o ln&'(temp) against '(time wor out the
gradient and use Arrhenius e!uation to calculate an activation energy
or the reaction. $or the catalyst I am looing to try dierent transition
metal catalysts# show their in"uence on the rate and determine which
one is the more eective on speeding up the reaction. And fnally I am
hoping with dierent acids show how the rate ormation o sulphur
precipitate changes with other acids and which one speed the
reaction up or slow it down.
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*hemical ideas:
+ The rate o reaction:
The rate o reaction is the measurement o how !uic a reaction
happens. It,s defned as the change in the amount o reactants or
products per unit o time or the time taen or the reactants to be
used up and the products to orm. Any actor that can increase the
number o successul collisions can increase the rate reaction. -e
have dierent methods to measure the rate o reaction on this
investigation I am going to use the disappearing cross method.
+isappearing cross:
This method measures the time taen or a precipitate to orm. A
glass o beaer is placed on top o a piece o paper with a blac cross
on it. The reactants are added to the beaer and a stopwatch started.
The stopwatch is then stopped when the cross is no longer visible.
This indicates the end point o the reaction with the precipitated ully
ormed.
+Activation energy:
The activation energy o a chemical reaction is the minimum energy
that must be input to a chemical system with potential reactants to
cause a chemical reaction. Activation energy can also be defned as
the minimum energy re!uired to start a chemical reaction.
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+Temperature on reaction rate:
$or a reaction to happen particles need to collide with enough energy#
increasing the temperature maes particles move aster which meansthat they will collide more re!uently and with more energy to mae
the reaction happen. Thereore we can say that increasing the
temperature increases the rate o reaction due to more collisions with
enough energy. This amount o energy needed to mae the reaction
happens is called activation energy. The /olt0mann distribution curve
&graph below) represents the distribution o molecular energies at a
constant temperature.
+*oncentration on reaction rate:
The rate o reaction measures the re!uency o successul collisions
between particles. The concentration is the amount o moles per unit
o volume o a chemical# so the more concentrated a chemical is the
more moles it will have thereore the more particles. Increasing the
number o particles in the same space will increase the the amount o successul collisions that occur that will also lead to an increase on
the reaction rate to increase. This means that as the concentration o
reactants increase rate o reaction will increase because o the
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Stephano Pina
increase o successul collisions due to the increase in particles.
+1ate e!uation and orders:
The rate e!uation lins the concentration o the reactants with the
rate o reaction. The rate o reaction depends on what is being
measured we could measure the rate at which reactants disappear or
the rate o which products are ormed. The overall rate e!uation
ollows:
-here A and / are the reactants or products depending on what is
being measured. The order o reaction tells you how the a reactantconcentration aects the rate. This can only be wored out rom
e%periment not rom chemical e!uations. The order can be ound by
using graphs either by plotting a concentration(time or
rate(concentration graph. The shapes o these will then allow you to
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Stephano Pina
determine the order.
+*atalyst:
A catalyst is a substance that,s speeds up a reaction but remains
unchanged at the end o the reaction. The catalyst provides an
alternative route or the reaction to happen with a lower activationenergy allowing more successul collisions at a lower energy and this
as a conse!uence maes the rate o reaction speed up. There are two
types o catalysts# homogeneous and heterogeneous. 2omogeneous
is the catalyst that is in the same state as the reactants whereas
heterogeneous catalysts are in a dierent state to the reactants.
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+Transition metals catalytic proprieties:
3any o the transition metals behave as catalysts this is due to their
variable o%idation number# which gives the capacity to tae and give
electrons and o%idi0e or reduce things easily. The ability o transition
metals to be in a variety o o%idation states# the ability to interchange
between the o%idation states and the ability to orm comple%es with
the reagents and be a good source or electrons mae transition
metals good catalysts.
+Acidity:
The strength o an acid or acidity is the ability o the acid to donate a
proton &24). A strong acid tends to dissociate completely in a solution
while a wea acid only dissociate partially.
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1is assessment:
+ '.& moldm-( ,ydrochloric acid: 5ow ha0ard# may cause harm
to eyes. 6ye protection and lab coat must be worn and small
amounts o it can be poured down the sin with water.+ & moldm-( odium thiosulphate: 5ow ha0ard but can cause
irritation in some cases eye protection and lab coat must be
worn.+ ulphur dio%ide diluted in water/: low ha0ard however the
given o gas is to%ic. 7se eye protection and lab coat and avoid
inhaling the umes i possible by woring on a ume cupboard or
wearing a aceguard.+ olid ulphur: low ha0ard. 6ye protection and lab coat must
be worn. Solid sulphur only causes minor ha0ard unless it is
heated. 8nly small !uantities can be put down the sin because
sulphur doesn,t dissolve in water.+ odium chloride: 5ow ha0ard. 5ab coat and eye protection
must be worn.+ '.& moldm-( 0ron 000/ chloride: low ha0ard. Still can cause
some irritation so lab coat and eye protection must be worn.+ Copper 00 sulphate: low ha0ard. 6ye protection and lab coat
must be worn.+ '.& and '.) moldm-( 0ron 000/ 1itrate: *an cause sin and
eye irritation. 6ye protection and lab coat must be worn.+ '.& moldm-( ulphuric acid: 5ow ha0ard. It may still cause
harm in the eyes or in a cut. 6ye protection and lab coat must
be worn.+ '.& moldm-( phosphoric acid: 5ow ha0ard. *an cause harm
on eyes. -ear lab coat and eye protection. *an be dispose
down the sin with lots o water.+ '.& moldm-( "ethanoic acid: 5ow ha0ard. *an be irritant
when in contact with eyes. 5ab coat and eyes protection must
be worn.+ '.& moldm-( 1itric acid: Irritant or eyes and sin. 5ab coat
and eye protection must be worn.+ '.& moldm-( ropanoic acid: low ha0ard. *an cause eye
irritation. 6ye protection and lab coat must be worn.+ 3ater: no riss.
8ther precautions:
+Any solution on poly bottle need to be labeled.
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+5ong hair must be tied bac.
+Apparatus must be rinsed and washed.
+9o to%ic products can go down the sin with water but all to%ic
products must go in the waste bottle.
3ethods:
"aing of standard solution of sodium thiosulphate:
6!uipment list:
Solid sodium thiosulphate
istilled water
'cm; beaer
' cm; volumetric "as
/alance &< d.p)
$unnel
3agnetic stirrer
"aing the standard solution:
$irst step is to calculate the mass o solid Sodium thiosulphate needed
to produce the volume needed in this case 'ml.
3oles: ' % '('= .' mol
3r o sodium thiosulphate: <>?.'?
3ass needed= .' % <>?.'?= <>.?< &<dp)
') 7sing a 'cm; beaer weigh out <>.?<g o sodium
thiosulphate# add about @cm; distilled water and use a
magnetic stirrer to mi% the solution together until all the solid is
dissolved.<) 7sing a unnel transer the solution made into the 'cm;
volumetric "as washing both the beaer and the unnel into
the volumetric "as so no solution is lost.;) Top up the volumetric "as to the 'cm; line with distilled
water. 3ae sure the bottom o the meniscus is resting on the
line. Then put the stopper on the top and shae it well to mi% allthe content eeping your thumb frmly on the stopper.
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>) Transer the solution to a poly bottle# label it maring the
concentration and volume and store it in a sae place to use it
when needed.
$%periment &:
Changing the concentration of sodium thiosulphate:
In this e%periment I used a disappearing cross method and changed
the concentration o sodium thiosulphate. -ith the recorded data I
plotted a concentration(time graph and a rate(concentration graph.
-ith this I hope to wor out the order o reaction with respect to
sodium thiosulphate and use it to later produce a rate e!uation.
6!uipment list:
'@cm; 2ydrochloric acid .' moldm+;
cm; Sodium thiosulphate solution 'moldm+;
Bcm; istilled water
;% 'cm; pipettes
;% '@cm; beaers
@% @cm; beaers
@% test tubes
/lac cross
Stopwatch
3ethod:
') $ill three dierent '@cm; beaers with sodium thiosulphate#
hydrochloric acid and water.
<) 7sing a 'cm; pipette fll @ @cm; beaers with 'cm; o 2*land fll @ test tubes with the amount o sodium thiosulphate and
distilled water shown in the table below using the other two
pipettes. 5abel the test tube ' to @ according to the e%periment
number.
6%pt -ater(cm; 'moldm+;
Sodium
thiosulphate(cm;
.'moldm+;
2ydrochloric
acid(cm;
' ' '
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< < ? '
; > B '
> B > '
@ ? < '
;) Place the frst beaer containing hydrochloric acid over the
blac cross and add test tube ' to it at the same time start the
stopwatch and swirl the solution to mi% the contents together.
1ecord the time taen or the cross to disappear in a table o
results. 1epeat this process mi%ing the other test tubes with the
rest o the beaers containing hydrochloric acid.>) 1epeat the process < times and also record the results.
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1esults:
6%pt Time'&s) Time<&s) Time;&s) Timeave&s)
' '@.<@ '>.? '>.> '@.;
< '.' '?.C? '?.?< '?.
; <C.B< <C.B <B.< <C.''
> ;C.<? ;B.B ;C.< ;?.
@ C>.C@ C@.< C>.' C>.?
Analysis:
1ate='(time
e%pt 1ate
' .BB@
< .@<
; .;B
> .<B;
@ .';>
$inding the concentration o each e%periment:
6%pt': n=' % &'(') =.'mol
6%pt<: n=' % &?(') = .?mol
6%pt;: n=' % &B(') = .Bmol
6%pt>: n=' % &>(') = .>mol
6%pt@: n=' % &<(') = .<mol
8verall concentration= moles(total volume
6%pt': n=.'( &<(') = .@moldm+;
6%pt<: n=.?( &<(') = .>moldm+;
6%pt;: n=.B( &<(') = .;moldm+;
6%pt>: n=.>( &<(') = .<moldm+;
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6%pt@: n=.<( &<(') = .'moldm+;
I have then used this data to plot a concentration(time graph and a
rate(concentration graph &graphs are attached to the page).
/y analysing the concentration(time graph we can see that the hallie o sodium thiosulphate is constant o ;'s# which indicates that
sodium thiosulphate should be frst order. The rate(concentration
graph also shows that the rate is directly proportional to the
concentration we can then conclude that sodium thiosulphate has a
frst order D9a<S<8;E'.
$%periment 2:
Changing the concentration of hydrochloric acid
In this e%periment I used a disappearing cross method and changed
the concentration o hydrochloric acid. I then used the data to I plot a
concentration(time graph and a rate(concentration graph. -ith this I
hope to wor out the order o reaction with respect to hydrochloric
acid and write a rate e!uation or the reaction.
6!uipment list:
'@cm; o ' moldm+; Sodium thiosulphate
cm; o .' moldm+; 2ydrochloric acid
Bcm; distilled water
;% 'cm; pipettes
;% '@cm; beaers
@% @cm; beaers
@% test tubes
/lac cross
Stopwatch
3ethod:
') $ill three dierent '@cm; beaers with sodium thiosulphate#
hydrochloric acid and water.
<) 7sing a 'cm;
pipette fll @ @cm;
beaers with 'cm;
o sodiumthiosulphate and fll the @ test tubes with the amount o
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hydrochloric acid and distilled water shown in the table below
with the other two pipettes. 5abel the test tube '+@ in relation to
the amount o solutions you have put in them.
6%pt -ater(cm; 'moldm+; Sodium
thiosulphate(cm;
.'moldm+; 2ydrochloric
acid(cm;
' ' '
< < ' ?
; > ' B
> B ' >
@ ? ' <
;) Place the frst beaer containing sodium thiosulphate over the
blac cross and add test tube ' to it at the same time start the
stopwatch and swirl the solution to mi% the contents together.
1ecord the time taen or the cross to disappear in a table o
results. 1epeat this process by mi%ing the rest o the beaers
with the other test tubes recording the time taen.>) 1epeat the process < times and also record the results.
1esults:
6%pt Time'&s) Time<&s) Time;&s) timeave&s)
' ';.? '>.< '>.<< '>.C
< 'B.' '@.C< '@.C@ '@.?;
; '?.< '?.?B '?.C@ '?.?>
> <>.C <>.< <>.'@ <>.'>
@ ;?.< ;C.C ;C.< ;C.C
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Analysis:
1ate= '(time
6%pt 1ate
' .C''
< .B;<
; .@>
> .>'>
@ .<B;
$inding the concentration o each e%periment:
6%pt': n=.' % &'(') =.'mol
6%pt<: n=.' % &?(') = .?mol
6%pt;: n=.' % &B(') = .Bmol
6%pt>: n=.' % &>(') = .>mol
6%pt@: n=.' % &<(') = .<mol
8verall concentration= moles(total volume
6%pt': n=.'( &<(') = .@moldm+;
6%pt<: n=.?( &<(') = .>moldm+;
6%pt;: n=.B( &<(') = .;moldm+;
6%pt>: n=.>( &<(') = .<moldm+;
6%pt@: n=.<( &<(') = .'moldm+;
I have then used this data to plot a concentration(time graph and a
rate(concentration graph &graphs are attached to the page).
/y analysing the concentration(time graph we can see that hal lie o
hydrochloric acid is not constant &'sF '@.@). This dierence in hal lie
can be the evidence that hydrochloric acid isn,t frst order since frst
order reactants have constant hal lie. /ut rom the
rate(concentration graph we can see that the rate is directly
proportional to the concentration indicating the hydrochloric acid has
a frst order. So by analysing my results and consulting my notes and
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because the dierence between the time o the hal lie &;.@s) is small
we can then assume that this dierence is due to errors on the
e%periment that I will later comment on the evaluation section. -e
can then conclude that hydrochloric acid is frst order D2*lE '. $rom the
previous e%periment we now that sodium thiosulphate is also frstorder# the rate o reaction is then frst with respect to each reactants.
-hich implies that the rate e!uation or this e!uation can be written
as r45,Cl6&51a22(6&.
$%periment (:
Changing temperature:
In this e%periment I used a disappearing cross method and tried the
e%periment at dierent temperatures. -ith the results I e%pect to
investigate the eect o the temperature on the reaction rate by
plotting a temperature(rate graph and a time(temperature graph. I
will also plot a ln&'(time)(&'(temperature) and use the Arrhenius
e!uation to fnd the activation energy o the reaction.
6!uipment list:
'cm; o .'moldm+; 2ydrochloric acid
Bcm; o ' moldm+; Sodium thiosulphate
>cm; distilled water
;% 'cm; pipettes
<% boiling tube
'% @cm; beaer
/lac cross
Stopwatch
Thermometer
>% <@cm; beaers
>% -ater baths &set to ;o# >o# @o# Bo)
3ethod:
') Into @ boiling tubes measure out 'cm; o hydrochloric acid
and place > o these into the water baths# one in each water
bath. Into another fve boiling tubes measure out ?cm; o
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water and <cm; o sodium thiosulphate and place > o them
into each o the our water baths.<) uring the time that the boiling tubes are in the water bath
add the boiling tube that is not in the water to a @cm;
beaer and place it on top o a blac cross. Put a
thermometer in the beaer then add the sodium thiosulphate
and water and start the stopwatch. 8nce the cross has
disappeared record the time and temperature.;) Tae the hydrochloric acid test tube in the frst water bath
and transer it to a @cm; beaer and place it on top o a
blac cross. Put a thermometer in the beaer then tae the
sodium thiosulphate and water solution on the water bath
and add it to the beaer. 8nce the cross has disappeared
record the time and temperature.
>) 1epeat stage ; or the beaers on the rest o the waterbaths.
@) 1epeat stages '+> again and record the results.
1esults:
Temperature&o*) Time'&s) Time<&s) timeave&s)
<; B?.@> C.; B.<
; >C.?> >?.< >C.;
;C ;<.?' ;<.C@ ;<.C?
>B '.?C <.; '.@
@C ';.<@ ';.;> ';.;
Analysis:
e%pt rate
' .'>>
< .<
; .;@
> .@'
@ .C@'
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$rom the e%periment and analy0ing temperature(rate and a
time(temperature graphs we can see that the time o reaction
decreases as the temperature increases# that means that rate
decreases when temperature goes up. -e can say that there is a
positive correlation between temperature and rate and a negativecorrelation between time and temperature. This means that by
increasing the temperature we increase the speed o the reaction and
thereore the rate. The higher temperature the aster the reaction
since the particles have more energy and are colliding more. -e can
then calculate the activation energy needed or the reaction to occur
using the ln&'(time)(&'(temperature) graph.
Activation energy= gradient % Ggas constant
5n&'(time) Temperature&H) '(T % '
;
+>.<> <B ;.;?
+;.?C ;; ;.;
+;.@ ;' ;.<;
+<. ;' ;.';
+<.@ ;; ;.;
$rom the graph:
radient= &+<.@4>.<)( &;.'%'+;+;.;C%'+;) = +>C<<
6a= gradient % G gas constant = +>C<< % ?.;' = ;<>' Jmol+'
;<>' Jmol+' is the activation energy that means that a particle should
have a minimum o ;<>'J in order to collide successully and cause
the reaction to happen.
$%periment +:
Adding a catalyst:
In this e%periment tried using dierent catalyst. -ith this I hope to
see their eect on the rate reaction and determine which one is more
eective on speeding the reaction up by putting the date on a bar
chart and comparing the results with the reaction without a catalyst.
6!uipment list:
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' cm; o .'moldm+; 2ydrochloric acid
'cm; o ' moldm+; sodium thiosulphate
>cm; o istilled water
>cm; o .'moldm+; Iron III chloride
>cm; o .'moldm+; *opper II sulphate
>cm; o .'moldm+; Iron III nitrate
>cm; o .@moldm+; Iron III nitrate
'% 'cm; beaers
'% boiling tubes
Stopwatch
/lac cross
<cm; pipette
<% 'cm; pipettes
3ethod:
') 7sing a pipette fll @ dierent beaer with 'cm;
o hydrochloricacid. 5abel these beaers with numbers rom ' to @.
<) $ill @ boiling tubes with 'cm; o sodium thiosulphate also
labeling it ' to @.;) 7sing a <cm; pipette measure out the dierent solution and
transer it to the respective test tubes:+<cm; o water to test tube '+<cm; o .'moldm+; Iron III chloride to test tube <+<cm; o .'moldm+; *opper II sulphate to test tube ;+<cm; o .'moldm+; Iron III nitrate to test tube >
+<cm;
o .@moldm+;
Iron III nitrate to test tube @
;) Tae beaer ' containing hydrochloric acid and place it over a
blac cross add test tube ' content to it mi% it and record the time
when the cross disappear.
>) 1epeat the same procedure mi%ing test tube < and beaer <# test
tube ; and beaer ;# test tube > and beaer > and test tube @ and
beaer @ always recording the time.
@) 1epeat the whole e%periment again recording the results to mae
it more accurate.
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6%pt 2*l(cm; 9a<S<8;(cm; 2<8(cm; *atalyst(cm;
' ' ' <
<#;#>#@ ' ' <
1esults:
6%pt Time'&s) Time<&s) Timeave&s)
' 9o catalyst 'B.'@ 'B. 'B.'<
< .'moldm+;
Iron III
chloride
'@.; '@.;C '@.;>
; .'moldm+;
*opper II
sulphate
'B.' '@.B@ '@.?;
> .'moldm+;
Iron III
nitrate
'B.C '@.@; '@.?
@ .@moldm+;
Iron III
nitrate
<.>@ <.'< <.<
Analysis:
@
'
'@
<
<@
;
;@
Catalyst
average time&s)
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Stephano Pina
The bar chart shows that the catalysts have a very low eect on
speeding the reaction up. The most eective o the catalysts on
maing the reaction aster is iron III chloride. .@moldm+; slows the
reaction down this is due to its high concentration and instead o
speeding up it has the opposite eect.$%periment ):
8i9erent acids:
In this e%periment I will use dierent types o acids to replace
hydrochloric acid. -ith the results I will plot a bar chart and determine
the ones who speed the reaction up and the ones that slow it down.
6!uipment list:
'cm; o 'moldm+; Sodium thiosulphate
<cm; o .'moldm+; sulphuric acid
<cm; o .'moldm+; phosphoric acid
<cm; o .'moldm+; propanoic acid
<cm; o .'moldm+; methanoic acid
<cm; o .'moldm+; nitric acid
<% 'cm; pipette
'% 'cm; beaer
'% boiling tube
/lac cross
Stopwatch
3ethod:
') 7sing a pipette fll @ dierent beaers with 'cm;
o sodiumthiosulphate labeling them rom ' to @.
<) 7sing another 'cm; pipette fll @ dierent boiling tubes with
the @ dierent acids labeling it also rom ' to @.+ $ill test tube ' with 'cm; o sulphuric acid+ Test tube < with 'cm; o phosphoric acid+ Test tube ; with 'cm; propanoic acid+ Test tube > with 'cm; methanoic acid+ Test tube @ with 'cm; nitric acid;) Place the beaer labeled ' on top o the blac cross. Add the
solution on test tube ' to it mi% it and record the time taen orthe cross to disappear.
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Stephano Pina
>) 1epeat that process mi%ing the beaers and test tubes with the
same label and recording the time taen to disappear.@) 1epeat the whole process &rom stage '+>) and record the
results.
1esults:
6%pt Time'&s) Time<&s) timeave&s)
' Sulphuric
acid
'.?' '.< '.?C
< Phosphoric
acid
<'.?? <'.<@ <'.@C
; Propanoicacid
''B.> ''?.>B ''C.;
> 3ethanoic
acid
@.;? @.'< @.<@
@ 9itric acid '>.?> '>. '>.?C
<
>
B
?
'
'<
'>
Acids
average time &s)
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Stephano Pina
/y analy0ing the bar chart we can see that sulphuric acid is the most
eective on speeding the reaction up and propanoic acid the less
eective. -e can also observe that the strongest the acid the aster
the reaction. This is due to the act that wea acids lie propanoic
acid and methanoic acid don,t dissociate completely and is harder toor them and re!uires more energy to give away the 24 that triggers
the reaction allowing the ormation o sulphur that causes the
precipitate to orm. That e%plains why a stronger acid will speed up
the reaction while a wea acid slows it down. Sulphuric acid also
contains sulphur and the presence o more sulphur in the reaction
maes it aster or the precipitate to orm because an e%cess o
molecules are involved in the process.
Conclusion:
$rom e%periment ' the frst graph shows us that sodium thiosulphate
has frst order has frst order in respect to the order o reaction as the
rate against concentration graph has produced a directly proportional
line and its hal lie is constant on the concentration against time
graph. 8n e%periment <# hydrochloric acid also appears to be a frst
order as the graph shows a directly proportional line or rate against
concentration even i the hal lie is not constant which is due to
errors that will be commented on the evaluation section that couldaect my results. -hich gives a overall order o reaction o < and a
rate e!uation r45,Cl6&51a22(6& . This means that both reactants
have one molecule reacting on the rate determining step. The results
rom e%periment ; o temperature change support the chemical idea
that the rate o reaction increases as temperature increases which
means that reaction happens aster. This also support the collision
theory that states the aster the molecules are moving more
molecules will have enough energy to successully collide and mae
the reaction happen. $rom that I plotted a graph and wored out theactivation energy or my reaction which was ;<>' Jmol+' which is the
minimum value o energy that a particle should have in order to
collide and react with success. $rom my e%periment > with the
catalyst we can see that transition metal catalyst have a small
increase in the speed o the reaction. -e can see that all the catalyst
used were heterogeneous and all e%cept rom .@moldm+; Iron III
nitrate made the reaction go aster. This catalyst eect o transition
metals is due to their unpaired electrons in the d orbital# and their
ability to orm a variety o o%idation states. This means they can
readily accept and(or donate electrons to orm intermediate
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Stephano Pina
compounds providing a dierent and aster path or the reaction to
tae place which e%plains why the reaction happened aster with the
addition o a catalyst. 8n e%periment @ we can see the dierent acids
and their eect on the reaction time. -e conclude that sulphuric acid
is the best acid to use in order to speed the reaction up this is due tothe presence o sulphur which maes the precipitate o sulphur to
orm !uicer due to the presence o more molecules and thereore
more probability o fnd sulphur molecules with enough energy to
react. The less eective acid is propanoic acid this is due to the act o
being a wea acid who doesn,t dissociate completely not providing 24
ions that can act has a catalyst on the ormation o sulphur.
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Stephano Pina
$valuation:
3aing o standard solution:
-hile maing the standard solution some procedural errors aecting
the results may have been made. -hen calculating the mass o
sodium thiosulphate is important to remember that it was hydrated
and it has to be included on the calculations. -hen rinsing the unnel
and beaer it is possible that some o the solution is let in the in the
beaer maing the moles o the solution not accurate and smaller
than e%pected. It is also very important that the bottom o the
meniscus is on the mar when water is added to the solution in the
volumetric "as because the concentration will not be correct and it
will aect the results. -hile measuring the mass o solid sodium
thiosulphate needed the <dp balance has an error o 4(+ .@g. The
precision error or measuring the solid will then be:
.@(<>.?<=.<'@ % ' = .<'@ K o percentage o error
The precision error or the 'cm; is 4(+ .;cm;
.; ( ' = .< % ' = .;K o error
*hanging concentrations:
In this e%periment some errors may have been incurred as I was using
a stop watch with precision error 4(+ .@s I could have started it at
dierent times allowing the reaction to start without a ull indication
to the actual time taen. -ith using the disappearing cross method it
was diLcult to Mudge the e%act time the cross disappeared and the
longer the reaction the harder it was to determine thereore stopping
the stopwatch at the same time was more diLcult maing my results
probably a ew seconds out. Also while mi%ing the reactions together
while timing them I may have mi%ed some more than others resulting
in a !uicer reaction. The change in room temperature on dierent
tries and dierent days was also a possible source o uncertainty
since a higher temperature can lead to a aster reaction and thereore
aecting the results o my e%periment. The 'cm; pipette used to
measure the solutions had a precision error o 4(+ .>cm;. The
percentage or each try is calculated below:
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Stephano Pina
6%periment ':
6%pt K o error rom
water reading
K o error rom
sodium
thiosulphate
reading
K o error
rom
hydrochlori
c acid
reading
K o error
rom
stopwatch
reading
' + .> .> .;;
< <. .@ .> .<B
; '. .BC .> .'?
> .BC '. .> .';
@ .@ <. .> .B?
6%periment <:
6%pt K o error
rom water
reading
K o error
rom sodium
thiosulphate
reading
K o error
rom
hydrochloric
acid reading
K o error
rom
stopwatch
reading' + .> .> .;B
< <. .> .@ .;<
; '. .> .BC .<C
> .BC .> '. .<'
@ .@ .> <. .';
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Stephano Pina
*hanging temperature:
In this e%periment some errors may have come rom the use o the
stopwatch while recording the time# the human reaction was the mainreason maing my time results probably be a ew seconds out.
Another source o error could be the act that I have only measured
the temperature at the end o the reaction instead o measuring the
beore and ater and mae an average. The thermometer I used to
measure the temperature also has a precision error o 4(+ .@o which
also adds some uncertainty to my measurements. The pipette used to
measure water# sodium thiosulphate and hydrochloric acid has a
precision error o 4(+ .>cm;. The percentage o error or each try is
listed below:
e%pt K o error
rom water
reading
K o error
rom
sodium
thiosulphat
e reading
K o error
rom
hydrochlori
c acid
reading
K o error
rom
stopwatch
reading
K o error
rom
thermomet
er reading
' .@ <. .> .C< <.<
< .@ <. .> .' '.C
; .@ <. .> .'@ '.>
> .@ <. .> .<@ '.'
@ .@ <. .> .;? .??
*atalyst e%periment:
Procedural error may have incurred as I used a stop watch# I could
have started it at dierent times allowing the reaction to start without
ull indication to the actual time taen. /y using the disappearing
cross method it is diLcult to Mudge the e%act point the cross ully
disappears and dierent persons can have dierent Mudgments aboutit adding or taing a ew seconds to the actual value o time. Also the
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Stephano Pina
longer the reaction taes the more diLcult is to stay concentrate on
stopping the stopwatch at the e%act moment. Another source o error
can be while mi%ing the solutions together and swirling it with more
or less orce maing some more mi%ed than others thereore aster or
the reaction to happen. The percentage o error or each try iscalculated below:
6%pt K o error
rom
water
reading
K o error
rom
sodium
thiosulph
ate
reading
K o error
rom
hydrochlo
ric acid
reading
K o error
rom
catalyst
reading
K o error
rom
stopwatc
h reading
' < .> .> + .;'
< + .> .> < .;;
; + .> .> < .;<
> + .> .> < .;<
@ + .> .> < .'C
ierent acids e%periment:
Procedural error may have incurred as I used a stop watch# I could
have started it at dierent times allowing the reaction to start without
ull indication to the actual time taen. /y using the disappearing
cross method it is diLcult to Mudge the e%act point the cross ully
disappears and dierent persons can have dierent Mudgments about
it adding or taing a ew seconds to the actual value o time. Also the
longer the reaction taes the more diLcult is to stay concentrate on
stopping the stopwatch at the e%act moment. Another source o error
can be while mi%ing the solutions together and swirling it with more
or less orce maing some more mi%ed than others thereore aster or
the reaction to happen. The percentage o error or each try is
calculated below:
6%pt K o errorrom sodium
K o errorrom acid
K o error romstopwatch
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Stephano Pina
thiosulphate
reading
reading reading
' .> .> .>B
< .> .> .<;; .> .> .>> .> .> .'@ .> .> .;>
References:
'. *lassroom notes<. A< level chemistry 8*1 / revision guide;. 1is assessment+ *leapss saety cheets>. http:((www.chemguide.co.u(physical(catalysis(introduction.html
<(<(<'@ dierent types o catalysts@. http:((en.wiipedia.org(wii(1eactionNrateNconstant 'C('(<'>@
reaction rate and rate constantB. http:((en.wiipedia.org(wii(1ateNe!uation 'C('(<'@ rate
e!uationC. http:((www.chemguide.co.u(physical(basicrates(catalyst.html
'C('(<'@ catalysts on rate reaction?. http:((www.chemguide.co.u(physical(basicrates(arrhenius.html
'?('(<'@ arrhenius e!uation. http:((www.ehow.com(aboutNBB?BC?Ntransition+metals+good+
catalystsN.html'. http:((en.wiipedia.org(wii(StandardNsolution '?('(<'@