Determination of the equilibrium constant for a chemical reaction
This chemistry lab report details an experiment to find the equilibrium constant of a reaction between iron (III) and thiocyanate ion. The process involved setting up laboratory equipment, mixing reactants in test tubes, and using a spectrophotometer to measure absorbance. The results confirmed the hypothesized equilibrium constant, demonstrating consistent values across different mixtures, showcasing the reaction’s dynamics under controlled conditions.
September 17, 2024
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Determination of the Equilibrium Constant for a Chemical Reaction
Student
Institution
Course
Professor’s Name
Date
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Determination of the Equilibrium Constant for a Chemical Reaction
Purpose of the Experiments
The main purpose of conducting this experiment is to determine the equilibrium constant
for a chemical reaction.
Abstract
The first procedure involved was setting up the laboratory equipment to conduct the experiments.
Each reactant’s solution was poured into five test tubes with 10 ml of volume. The respective
reagents were mixed and stirred to ensure they dissolved proportionally. Afterward, the
spectrophotometer was used to determine the volume of the absorbance. Finally, the
concentration for each product was determined and used to determine the value of the
equilibrium constant. The objective of the experiment was achieved since the value of the
constant of equilibrium for each volume of reactants and product was the same.
Introduction to Equilibrium Constant
In most instances, whenever a chemical reacts, the reaction does not halt; rather, it is
subjected to other intermediate states where the reactant and product have a concentration that is
not affected by time. This state where the concentration is not affected is called chemical
equilibrium. Therefore, the law of equilibrium demands that the ratio of the reactant and products
should be equal to the ratio of some constant for the reaction (Rodríguez. et al., 2021). This
experiment will focus on studying the equilibrium properties of a chemical reaction between iron
(III) and and thiocyanate ion, .Hypothetically speaking, it is believed that the
equilibrium constant for all reactants and products should be the same.
KC
Fe3+
SCN−
3
Procedures of the Experiments
1. Take five test tubes and label them. The test tubes are labeled according to numbers one
to five or as indicated in the test tube rack.
2. Pour 30Ml of M Fe ( ) 3 into a dry 100ml beaker. Ensure you
pour out the solution into the beaker while observing the accuracy of the volume
3. Add another 20ml of M KSCN into another beaker dry beaker. This is
done carefully with the appropriate volume of KSCN.
4. Pipet 1.00, 2.00, 3.00, 4.00, 5.00 Ml from KSCN beaker to respective test tubes. The
pipet is done for the respective solution while mixing the solution.
5. Pipet the approximate Ml of water to each test tube so that the total volume will be 10ml
6. Add respective reagents to the respective and ensure you stir the mixture properly.
7. Place a small mixture in test tube 1 in a spectrophotometer and determine the absorbance
value at 447 nm.
8. Obtain the concentration of from the calibration curve or the equation and
record the values
9. Prepare a solution of a known concentration by pipetting 10.00ml of a special
Calibration solution
Steps of Calculating the Equilibrium constant
1. The following steps were used in the determination of the equilibrium constant.
2. The initial number of moles for the reagents was obtained using the molarity of a
respective solution.
3. The number of moles of the product formed was determined
2.00 × 10−3
NO3
2.00 × 10−3
FeSCN2+
FeSCN2+
4
4. The number of moles of reagents that were present in the equilibrium was obtained
5. The concentration for each of the species that were present in the equilibrium was also
calculated
6. The value of the constant K was obtained using the formulae.
Raw Data
The following data from the experiments will be used to calculate moles and equilibrium
constant.
Table 1: Respective Tubes of the Water Added and the Reactants
Respective Test tube number
1
2
3
4
5
5
5
5
5
5
Vo l u m e o f
KSCN
1
2
3
4
5
The volume
o f w a t e r
added
4
3
2
1
0
The volume
of Fe ( )
3
NO3
5
Table 2: Respective volumes of the mixtures and absorbance
Calculation of the Equilibrium Constant
The number of moles is calculated by the formulae:
Therefore, for each solution, we can calculate the moles of each solution as demonstrated in table
3 below.
Mixture
Volume of
water(ML)
M e t h o d 1
Absorbance
1
5.00
1.00
4
0.108
2
5.00
2.00
3
0.194
3
5.00
3.00
2
0.241
4
5.00
4.00
1
0.330
5
5.00
5.00
0
0.463
Volume of
KSCN(ML)
2.00 × 10−3
1 . 210 ×10−4
0 . 862 ×10−4
M
0 . 282 ×10−4
0 . 630 ×10−4
0 . 507 ×10−4
Volume of
M F e
( )
2.00 × 10−3
NO3
FeSCN2+
MA=MolesA
Volumeofsolution,v
MolesA=MA × Volume
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Table 3: Respective values of moles obtained
Conclusion
From the tables, it is seen that the moles of the reactants and products are the same.
Hence the constant of equilibrium for each product is the same. Therefore, the aim of the
investigation was achieved, and the outcomes can be used to conduct further analysis.
Respective Test Tube Number
1
2
3
4
5
5
5
5
5
5
Moles SCN
Vo l u m e o f
KSCN
1
2
3
4
5
The volume
o f w a t e r
added
4
3
2
1
0
20.00 × 10−6
20.00 × 10−6
The volume
of Fe ( )
3
NO3
20.00 × 10−6
M o l e s o f
Fe2+
20.00 × 10−6
20.00 × 10−6
7
Reference
Rodríguez de San Miguel, E., González-Albarrán, R., & Rojas-Challa, Y. (2021). Conditional
equilibrium constants reviewed. Critical Reviews in Analytical Chemistry, 1-23. C
September 17, 2024
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Academic level:
Undergraduate 3-4
Type of paper:
Lab report
Discipline:
Chemistry
Citation:
Not Applicable
Pages:
5 (1375 words)
* The sample essays are for browsing purposes only and are not to be submitted as original work to avoid issues with plagiarism.
