TITLE:
KINETICS CHEMICAL
DAY/DATE:
MONDAY, APRIL 20 2017
PRACTICAL
OBJECTIVES:
a)
Measures changes in the concentrations
of reagents by time
b)
Observe the effect of concentration,
temperature, and catalyst on reaction rate
c)
Determining the rate laws of a reaction
in an aqueous solution
Theoretical basis:
Reaction rate
measurement is an amazing chemical field. From kinetic studies, the mechanism
of the reaction can be reduced. Information about the reaction of catalysts and
inhibitors can only be obtained through kinetic assessment.
The rate of a chemical
reaction can be affected by several factors:
a.) The
concentrations of reagents (and sometimes products)
b.)
Temperature
c.)
Catalyst
Rate
measurements are usually performed under fixed experimental conditions, with one
fixed factor whereas other factors are varied. When the influence of these
factors on the rate has been determined, these factors are fixed and other
factors are varied. Systematic assessment of rate dependence on reaction rate
changes is continued until the kinetic behavior of the reaction is complete.
How
to measure the rate of reaction, one important aspect of kinetic assessment is
to design an easy technique to monitor the course of the reaction over time.
Chemical analysis by means of volumetry or gravimetry is relatively slow, so
this way is not in use unless the reaction is slow, or can be stopped by sudden
cooling, or by the addition of reactants that stop the reaction.
Some
commonly used ways are to use the nature of color and conductivity. The reaction
rate involving the gas is determined by measuring the volume of time union gas.
In this experiment you use a color change.
For a hypothetical reaction
2A + 3B à C + 5D
The
law of its speed can be
Where
k is the rate constant; N is the reaction order for A; And m is the reaction
order for B. The overall reaction order is n + m. The order of the reaction can
only be determined by experiment, since these numbers are not always the same
as the reaction coefficient (stoichiometry).
In
this experiment you will perform a reaction between sodium thiosulfate with
hydrochloric acid.
S2O3-2
+ 2H+ à SO2
+ H2
The
rate of this reaction depends only on the concentration of S2O3-2, but not on
the acid concentration. This is evidenced from the graph 1 / t against (S2O3-2)
which gives a straight line. This graph implies that the order of reactions is
one for thiosulfate. And because the acid concentration does not affect the
rate. The rate of the org is zero.
You
will also experiment with a two-order reaction for one of the reacting
components. Second order can be inferred when a straight line is formed from
graph 1 / t against [HCl] 2 (Basic Chemistry lab guide,
2011: 71-72).
Chemical
reactions are the process of turning the reagents into reactions. The process
is slow and there is fast. For example gasoline burns faster than kerosene.
There are very fast reactions, such as burning dynamite that produces an
explosion, and a very slow one is like a rusting process of iron. The
discussion of the rate (rate) of the reaction is called chemical kinetics. In
this chemical kinetics put forward how to determine the rate of reaction and
what factors influence it(Syukri,1999:85).
Reaction
kinetics is a branch of chemistry that discusses the rate of reactions and
influencing factors. The rate (velocity) of the reaction is expressed as a
change in the concentration of reactant or reaction product to the unit of
time. The reaction rate of a reaction can be expressed by the rate equation of
the reaction, for the following reaction:
A+B à AB
The
reaction rate equation is generally written as follows:
R
= k [A]m[B]n
K
as the reaction rate constant, m and n the partial order of each reactant
(petrucci,1987:134).
Order
is concerned with rank in law of reaction rate. The constant reaction, not
dependent on the concentration of the reactant is called the zero reaction
order. The first-order reactions are more likely to exhibit a single
concentration in the law of the rate, and the concentration is one rank. The
most common formulation of the two-order reaction rate law is a single
concentration of two or two concentrations of each of the first ranks. One
method of determining reaction order requires measurement of the initial
reaction rate of the experimental experiments. The second method requires
precise mapping of the reactant concentration function over time. To get a
straight line graph (Hiskia, 1992: 213).
TOOLS AND
MATERIALS
Tool
a) Erlenmeyer
b) Stopwatch
c) Pipette
drops
d) Sandpaper
Steel
e) Pumpkin
f) The
reaction tube
g) Measure
Glass
h)
Watershed
Material
a) Tiosulfate
solution
b) Water
c) Hydrochloric
Acid
d) Na2S2O3
e) HCl
f) Mg
Band
g) Oxalic
acid
h) Sulfuric
acid
i) KMnO4
j) H2SO4
WORK PROCEDURES
Order
of reaction in reaction of sodium thiosulfate with hydrochloric acid
1.) in preparing the reagents, first mix the thiosulfate solution with water before the hydrochloric acid is added
1.) in preparing the reagents, first mix the thiosulfate solution with water before the hydrochloric acid is added
2.)
turn the erlenmeyer to make the mixture really homogeneous
3.)
recorded the start time when the acid is added until the occurrence of
turbidity due to deposition of sulfur. Anyone can think differently about when
the turbidity arises, so set the timing method. Which performed two
replications
4.)
is carried out by experiment of the mixed composition, the volume of thiosulfate
is fixed, and the acid volume is varied
Mixed
composition in the determination of the reaction order for sodium thiosulfate
|
Na2S2O3
(ml)
|
[Na2S2O3]
(M)
|
H2O
(ml)
|
HCl (ml)
|
|
25
|
0.15
|
-
|
4
|
|
20
|
0.12
|
5
|
4
|
|
15
|
0.09
|
10
|
4
|
|
10
|
0.06
|
15
|
4
|
|
5
|
0.03
|
20
|
4
|
Composition
of the mixture in the determination of the reaction order for the acid,
hydrochloride
|
Na2S2O3
(ml)
|
H2O
(ml)
|
HCl (ml)
|
HCl (M)
|
|
25
|
-
|
5
|
3.0
|
|
25
|
2
|
3
|
1.8
|
|
25
|
4
|
1
|
0.6
|
B.
Order of the reaction in reaction between magnesium and hydrochloric acid
1.)
cleaned Mg band with steel emery, and splice it into 16 pieces of 2 cm in
length. Inserted each 1 piece of metal into the 8 erlenmeyer provided, set
aside 8 other pieces.
2.)
diluted 2 M HCl solution. Dilution was carried out in a 100 ml 100-meter flask.
Poured 100 ml of acid solution into erlenmeyer and recorded time with stopwatch
3.)
wiggle erlenmeyer to keep magnesium fixed
4.)
stopwatch stopped after Mg dissolves
5.)
repeat the experiment by re-inserting another Mg piece into the same acid
solution. Recorded time
Mg mixture composition with HCl
Mg mixture composition with HCl
|
HCl (M)
|
Volume HCl (ml)
|
|
0.6
|
100
|
|
0.8
|
100
|
|
1.0
|
100
|
|
1.2
|
100
|
|
1.4
|
100
|
|
1.6
|
100
|
|
1.8
|
100
|
|
2.0
|
100
|
C.
Effect of temperature on reaction rate
1.)
taken 6 tubes of reaction, filled each with 8 ml of oxalic acid 0.1 N and 2 ml
of 6 N sulfuric acid
2.)
prepared 3 cup goblet, half filled with water. The first cup was boiled, the
second cup was heated to 50 degrees Celsius, and the third cup was not heated
3.)
2 tubes inserted into each cup, after 10 minutes, into each tube added 3 drops
of KMnO4 0.1 N. note the color change and recorded time and reaction in each
tube.
D.
Effect of catalyst on reaction rate
1.)
taken 6 test tubes, filled with 6 ml of oxalic acid solution
a.
Tube 1 dn 2 each added 2 ml H2SO4 1 M
b.
Tube 3 and 4 are each added 1 ml of
H2SO4 1 M
c. Tubes
5 and 6 were each added 4 ml of H2O
2.)
into each tube give 3 drops of KMnO4
3.)
Note the color change and recorded reaction time
OBSERVATION DATA
A.) Order
of reaction in the reaction of Sodium thiosulfate with hydrochloric acid
Observation on the effect of Na-thiosulfate concentration
Observation on the effect of Na-thiosulfate concentration
|
Na2S2O3 (ml)
|
Na2S2O3
(M)
|
H2O (ml)
|
HCl (ml)
|
T
|
1/t
|
|
25
|
0.15
|
-
|
4
|
127
|
0,00787
|
|
20
|
0.12
|
5
|
4
|
160
|
0,00625
|
|
15
|
0.09
|
10
|
4
|
198
|
0,00505
|
|
10
|
0.06
|
15
|
4
|
86
|
0,00349
|
|
5
|
0.03
|
20
|
4
|
319
|
0,000313
|
The order of the
reactions is 1 for Na2S2O3
Observation on
the effect of hydrochloride acid concentration
|
Na2S2O3
(ml)
|
H2O
(ml)
|
HCl (ml)
|
[HCl] (M)
|
T
|
1/t
|
|
25
|
-
|
5
|
2.0
|
78
|
0.0128
|
|
25
|
2
|
3
|
1.8
|
96
|
0.0104
|
|
25
|
4
|
1
|
0.6
|
102
|
0.0098
|
B.)
Orde reaction in magnesium reaction with
hydrochloric acid
Observation
on the effect of hydrochloride acid concentration
|
[HCl] (M)
|
HCl (ml)
|
t
|
1/t
|
[HCl]2
|
Log [HCl]
|
Log (1/t)
|
|
0.6
|
100
|
414
|
0,002415
|
0,36
|
-0,221
|
-2,617
|
|
0.8
|
100
|
343
|
0,002898
|
0,64
|
-0,0960
|
-2,537
|
|
1.0
|
100
|
202
|
0,004545
|
1,44
|
0
|
-2,342
|
|
1.2
|
100
|
130
|
0,00769
|
1,44
|
1.08
|
-2,114
|
|
1.4
|
100
|
88
|
0,01136
|
1,96
|
1.15
|
-1,945
|
|
1.6
|
100
|
55
|
0,01818
|
2,56
|
1.20
|
-1,740
|
|
1.8
|
100
|
40
|
0,025
|
3,24
|
1.25
|
-1,602
|
|
2.0
|
100
|
25
|
0,04
|
4
|
1.30
|
-1,398
|
C.)
The temperature effect on the reaction
rate
Reaction time at
various temperatures (sec)
|
Repeat
|
Reaction
temperature
|
||
|
1000C
|
500C
|
250C
|
|
|
1
|
2s
|
13s
|
33s
|
|
2
|
2s
|
13s
|
33s
|
|
average
|
2s
|
13s
|
33s
|
Signs of reaction: a change of color to
a clear white
D.) The
effect of the catalyst on the reaction rate
|
Repeat
|
H2SO4
|
||
|
2ml
|
1ml
|
0ml
|
|
|
1
|
2 minute 33Seconds
|
12 minute 4 Seconds
|
23 minute 90 Seconds
|
|
2
|
2 minute 41Seconds
|
15 minute
|
24 minute 15 Seconds
|
Signs of reaction:
1.) 2ml
→ purple disappear (purple-purple-red liver-orange nodes) heat reaction
2.) 1ml
→ purple disappear (purple-purple-red heart-orange nodes) heat reaction
3.) Purple,
fixed homogeneous solution
RESULTS AND
DISCUSSION
A.) Order
of reaction in reaction of sodium thiosulfate with hydrochloric acid
In
this experiment we observed a reaction order between the thiosulfate solution
and hydrochloric acid. In the determination of the order of this reaction is
closely related to the rate of reaction. In general, the rate of reaction is
defined as the change in reagent concentration and reaction product per unit
time. Chemically, the rate of the reaction is determined by determining the
concentration of the substances at a given time, then the concentration data is
used to calculate the reaction rate.
In
this experiment, we can determine the reaction order of each reaction reactor
according to the reaction rate data. For reactions:
Na2S2O3
(aq) + 2HCl (aq) à2NaCl (aq) + SO2 (g) + S (s)
In
this experiment the thiosulfate solution was mixed with water, then
hydrochloric acid was added. After mixing homogeneously, the experiments as
listed in Table 10.1 and the results of the observations are as follows:
a.
25 ml of Na2S2O3 with 0.15 M mixed with 4 ml of HCl. Within 127 seconds the
solution has shown turbidity, due to the deposition of sulfur. In this first
experiment the compound did not add water to the sodium thiosulfate. This
incorporates a faster mass to appear entirely in the solution when added with
water or not with water.
b.
20 ml of Na2S2O3 with 0.12 M mixed with 5 ml of H2O, then added with 4 HCl.
Within 160 seconds the solution has shown turbidity, due to sulfur deposition
at the bottom of the erlenmeyer tube.
c.
1.5 ml of Na2S2O3 with 0.09 M mixed with 10ml H2O, then added with 4 ml of HCl.
In 198 seconds the solution has shown turbidity, due to the deposition of
sulfur at the bottom of the erlenmeyer tube.
d.
10 ml of Na2S2O3 0.06 M mixed with 15 ml of H2O, then added with 4 ml of HCl.
Within 286 seconds the solution has shown turbidity, due to the deposition of
sulfur at the bottom of the erlenmeyer tube.
E.
5ml Na2S2O3 0.03 M mixed with 20 ml of H2O, then added with 4 ml of HCl. Within
319 seconds the solution has shown a turbidity due to sulfur precipitation at
the bottom of the test tube.
Theoretically,
for experiments with the mixed compositions listed in Table 10.2, we only
searched for the order of reactions alone and calculated the overall reaction
order.
Order of reactions in the reaction of magnesium and hydrochloric acid
Order of reactions in the reaction of magnesium and hydrochloric acid
For
reaction = Mg (s) + 2 HCl (aq) à MgCl2 (aq) + H2 (g)
The
treatments given in this reaction are:
a.
Comparison of various HCl concentrations (0.6 M; 0.8 M; 1.2 M; 1.4 M; 1.6M;
1.8M; and 2M). At the same volume of HCl and react the Mg band into the test
tube. The observation result of bubble gas and magnesium dissolve in HCl until
exhausted in a certain time.
b.
Magnesium takes several minutes to dissolve in HCl where the speed depends on
the concentration of the HCl
c.
The rate of reaction is influenced by varying HCl concentrations.
For
example, the reaction rate equation is formulated by r = k [Mg] [HCl], the rate
of reaction depends only on the solution phase [HCl] so that the reaction order
to Mg is zero.
Effect
of temperature on reaction rate
As
has been known before that the temperature rise accelerates the reaction,
otherwise the decrease in temperature will slow the reaction. In the case of
reaction
rates:
A2 + B à 2AB has the equation: r = k [A] m [B] n
The
temperature change has k, since its value depends on the temperature and the
type of reaction. If the temperature is raised, the amount and energy of
collisions between reagent molecules increases.
B.) Effect of catalyst on reaction rate
A
slow reaction can be accelerated by giving / adding other substances without
adding concentration or temperature. The substance is called a catalyst. The
catalyst usually reacts temporarily and then re-forms as a free agent. Next
reacts again with the reactant speeding up the reaction and free again. So on
and on over and over again.
A
reaction using a catalyst is called a catalyst reaction and the process is
called catalysis. The catalyst of a reaction is usually written over an arrow.
Example:
2KCl
(g) MnO2 2KCl (s) + 3O2 (g)
DISCUSSION
Order
reaction in reaction of Sodium Tiosulfate with hydrochloric acid
In
the observation experiment on the effect of Na-thiosulfate concentration, we
used Na2S2O3 with different amount of volume, as well as H2O volume, different
but the volume of HCl was fixed. This experiment works, because we can prove
the order of the reaction, where the reaction order is x = 1.
In addition, in subsequent experiments observation of the effect of concentration on hydrochloric acid, also obtained the order of reaction is 0.26. Thus we can calculate the overall reaction order is 1.26.
In addition, in subsequent experiments observation of the effect of concentration on hydrochloric acid, also obtained the order of reaction is 0.26. Thus we can calculate the overall reaction order is 1.26.
A) Order
of Reactions in magnesium reaction with hydrochloric acid
in
this experiment we observed the effect of hydrochloric acid concentration, just
as our previous experiments used HCl with the same amount of volume, but the
molarity was different. A total of 8 experiments. And the results of the
experiments obtained are the higher the concentration of HCl used to react the
Mg band, the faster the rate of reactions.
B) Effect
of temperature on reaction rate
In
this experiment, we have proven that the temperature affects the speed of
reacting a substance, where the reaction signals that occur are the occurrence
of discoloration.
From the literature gained, the temperature rise accelerates the reaction, and otherwise the decrease in temperature slows the reaction. Judging from the rate of reaction, for example A + B + C à result, has an equation
From the literature gained, the temperature rise accelerates the reaction, and otherwise the decrease in temperature slows the reaction. Judging from the rate of reaction, for example A + B + C à result, has an equation
V
= k [A] m [B] n [c] 0
The
temperature change has k, since its value depends on the temperature and the
type of reaction, increased then the amount and the collision energy between
reagent molecules increases.
In
addition, the reaction can take place in the event of a direct collision
between reagent molecules. This collision must meet two conditions namely its
position is effective and sufficient energy.
C) Effect
of catalyst on reaction rate
In
this experiment, we tested the effect of the catalyst on the reaction rate of a
solution and this experiment was successfully performed with the signs of
reaction is the occurrence of discoloration.
Slow
reaction can be accelerated by giving other substances without increasing the
concentration or temperature. This substance is called a catalyst. A reaction
using a catalyst is called a catalyst reaction and the process is called
catalysis. Based on the phase, the catalyst can be divided into two, namely
homogeneous and heterogeneous.
CONCLUSION
From
the experiments conducted, it can be deduced:
The
effect of time on the change of reagent concentration is the more time, the
reagent concentration decreases.
Effect
of temperature, concentration and catalyst on the reaction rate, the higher the
temperature in the reaction, the faster the reaction rate will be. Similarly
with concentration, the greater the concentration the faster the reaction rate,
and the more the catalyst inserted into a reaction the greater the
concentration the reaction rate will accelerate
A
reaction using a catalyst is called the catalyst reaction and its pro- cess is
called catalysis. By phase, the catalyst can be divided into two: homogeneous
and heterogeneous catalysts
BIBLIOGRAPHY
Epinur,
dkk.2010.P Basic Chemical Practical Guide.Jambi: Jambi University
Hiskia,
A and Tupamalu. 1992. Electrochemistry and Chemical Kinetics. Bandung: ITB
Petrucci,
Ralph H.1987. Basic Chemistry Principles and Applied Modern Volume 2. Jakarta:
Erland
Syukri
S, 1999. Basic Chemistry 2. Bandung: ITB
BalasHapusDescribe the factors that affect the reaction rate you write above?
Factors affecting reaction rate:
Hapus1. Change of concentration / Concentration of reagents
The thicker the concentration of reagent substances the possibility of collisions between molecules of substance the more frequent collisions
2. Reaction temperature / temperature change
At higher temperatures, the molecule "moves faster because the kinetic energy of the substance molecule increases, making it more likely that collisions between molecules of reactants
3. Pressure / Volume
At higher temperatures the volume becomes smaller so that the particles "become closer and more collisions occur.
4. Surface area
The more surface area the faster the reaction
5. Catalyst
Catalyst: a substance which can speed up a type of reaction
Its nature: the catalyst will decrease the activation energy, that is the minimum energy that must be possessed by the substance in order for the reaction to take place.
The more catalysts the easier the reaction will be
What is the difference of reaction rate andreaction order?
BalasHapusThe reaction rate or reaction rate indicates the number of chemical reactions that take place per unit of time. The reaction rate represents the molarity of the solute in the reaction produced per second of the reaction.
HapusThe reaction sequence, for example in the transport of electrons or the sequence of the oxidation-reduction step, will be explained by the chain or stages.
why you use KMnO4 in your experiment?
BalasHapusBecause KMnO4 is useful as a catalyst, the catalyst is a substance that accelerates the rate of reaction of a chemical reaction at a certain temperature, without undergoing change or being used by the reaction itself
Hapus"Mix the thiosulfate solution with water before the hydrochloric acid is added", why should so?
BalasHapusBecause Hydrochloric acid is an aqueous solution of hydrogen chloride gas (HCl). It is a strong acid, and is a major component in gastric acid. These compounds are also widely used in industry. Hydrochloric acid should be handled with appropriate safety wewanti as it is a highly corrosive liquid.
Hapus
BalasHapusWhat are the learning materials related to chemical kinetics?
Learning materials related to chemical kinetics such as rate law, rate constant, reaction order, activation energy, and reaction order
HapusHow to experiment on the effect of Na-thiosulfate concentration ?
BalasHapusSodium thiosulfate is a hydrated salt with a chemical formula Na2S2O3, a colorless crystalline solid, dissolves in water, and can act as a reducing agent, shiny in moist air and bloom in dry air at temperatures greater than 33 ° C. The solution is neutral or weak base to litmus. Very soluble in water and insoluble in ethanol. Sodium thiosulfate also acts as an antidote to cyanide poisoning.
HapusThiosulfic acid can not be formed by adding acid into thiosulfate because of the decomposition of this free acid in water in this mixture of S, H2S, H2Sn, SO2, and H2SO4 can be made by removing water, in low temperature (780C).
In the mixture thiosulfate salts are stable and acidic. Tiosulfates are prepared by boiling alkali or a solution of sulfate nitrate with S and also oxidation of the polysulfide by air. The salt commonly called thiosulfate is stable and large amounts.
Sulfites and other soluble metals are very small or insoluble. Hydrogen sulfite from alkaline earth metals is known only in solution. Sulfur has similar properties with oxygen, among others, that is, they form ionic compounds with active metals and both form covalent compounds such as H2S, H2O, CS2, SCl2, and Cl2O. However, some of the factors that make a difference include the single covalent bond length of O is 74 pm and S is 104 pm, the electronegativity of O is 3.5 and S is only 2.6.
The thiosulfate ions are similar to sulfate ions except that one of the oxygen is replaced by a sulfur atom (tio-is a prefix meaning sulfur). These two sulfur atoms have an entirely different environment. "Additional" sulfur atoms act similarly as sulphide ions. The oxidation rate for central sulfur atoms is +5, whereas for "extra" sulfur atoms is -1. Sodium thiosulfate pentahydrate can be prepared easily by educating sulfur in a sulfite solution according to the reaction equation:
SO32- (aq) + S (s) ® S2O32- (aq)
How does the catalyst effect on the reaction rate?
BalasHapusThe catalyst is a substance that accelerates the rate of reaction. The catalyst serves to decrease the activation energy so that the reaction rate will accelerate.
HapusThe catalyst is a substance that acts to speed up the process of chemical reaction but it does not participate in the process
The more the catalyst is added the faster the chemical process is complete
In other words, the effect of the catalyst on the rate of reaction lies in its role in reducing the activation energy of the catalyst to minimize the activation energy, so that many particles having greater kinetic energy than the activation energy and reaxion progress more quickly
If in your practicum fails but time is running out what are you doing?
BalasHapusIf in my practicum I did and failed, but the time was running out, I would continue my pratikum and record or discuss the failure in the report, and I would look for literature as a counterpart to the failure result at the time of the lab
HapusWrite the rate formula for the following reaction in terms of the loss of reactants and the appearance of the product:
BalasHapus1. I- + OCl- -> Cl- + OI
2. 3O2 -> 2O3