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Project 4: Equilibrium

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Goumi Gokul

on 12 April 2017

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Transcript of Project 4: Equilibrium

Project 4: Equilibrium
Background: Equilibrium is found in our day to day life. It is mainly associated with the word balanced, and it is widely used in many different subjects such as chemistry, physics, biology, and more. There are a plethora of examples relating to Equilibrium such as a balanced seesaw with people of the same weight are on both ends, a hot cup of coffee cooling down to room temperature, when the concentration of the products and reactants are constant after a chemical reaction and much more (Pakoraz).
Theory: Some concepts that should be known for the better understanding of this lab are: absorbance, equilibrium, calibration curve, spectroscopy, and acid-base reaction. It is known that as concentration increases, absorbance also increases.
Hypothesis/Objectives: The objective for both weeks of this lab was to determine the equilibrium constant for a complex Fe(SCN)^2+ using spectroscopy and the cncentrations calculated. The hypothesis we formulated was that as the concentration of Fe(SCN)^2+ increases, there should be a constant increase in absorbance between all the test tubes.
Methods Part 1
• Gathered materials.

• Measured out 0.0486 g of 0.002M KSCN

• Filled base of volumetric flask with HNO3, then added the 0.0486 g 0.002M KSCN to the flask. Then filled to the 250 mL line with 3M HNO3.

• Next 30 ml of the 0.002M KSCN solution, 50 mL of 3M HNO3, and 30 mL of 0.2M Fe(NO3)3 were measured out and placed in separate beakers.

• Next 5 test tubes were filled with 2.5 mL of 0.2M Fe(NO3)3 using a graduated pipette.

• Next varied amounts of 0.002M KSCN were added to each test tube. (Refer to Table 1).

• Then the 3M HNO3 was added till there was 10 mL of solution in each test tube.

• Then parafilm was placed on the test tubes to mix them well. The absorbance was measured for each using the ocean optic spectrophotometer.

• First the spectrophotometer was standardized with 3M HNO3. Then the cuvettes were filled to the tip of the triangle, wiped down with Kimi wipes and tested.

• Finally, the data was used to make a standard curve of Absorbance vs. Fe(SCN)⁺².
From graph y=3800x-0.168
Tube 1: 0.15=3800x-0.168=> 5.7*10^-5
Tube 2: 0.16=3800x-0.168=> 7.05*10^-5
Tube 3: 0.17=3800x-0.168=> 9.68*10^-5
Tube 4: 0.20=3800x-0.168=> 1.3*10^-4

During both weeks the concentrations of different chemicals were determined spectrophotometrically according to the absorbance and the standard curve created.
Research Connection
• Gathered materials.

• First 8.33 mol of 3M HNO3 were measured out and placed in a volumetric flask.

• Then the flask was filled to the 250 mL line with deionized water. Then 50 mL of the solution was measured out and placed in a beaker.

• Then 30 mL of 0.002M KSCN and 0.002M Fe(NO3)3 were measured out and placed in separate beakers.

• Next 5 mL of 0.002M Fe(NO3)3 was added to 5 test tubes using a graduated pipette.

• Then varied amounts of 0.002M KSCN were put in the test tubes. Then 3M HNO3 was added to each test tube to total 10 mL of solution in each one. (Refer to Table 2).

• Each test tube was then covered with parafilm and mixed.

• Then the absorbance of each test tube was recorded using the same process as methods one with the spectrophotometer.

• A standard curve was made from the absorbance, same as part 1.

• Finally, using ICE Tables, the Keq was calculated for each test tube and compared to the theoretical Keq for Fe(SCN)⁺².
Sources of Error
• Test tube 4 did not fit the linear curve. The solution was remade, but the results were the same. We were not able to pinpoint the error, so the values are off (not completely linear trendline).

• Our spectrophotometer was not working. We had to use several to obtain accurate results. The results may not be that accurate because three different spectrophotometers gave us three different sets of data.

• Test tube 5 in methods part 2 was also off. Instead of increasing the absorbance drastically decreased. This could be due to the test tube being dirty. It was remade, but the data was still off. Therefore, it was ignored and not placed on the linear curve.
• Laboratory coats, splash proof goggles, and gloves were worn at all times during the lab. Wear proper PPE.

• When the experiment was ended, the group washed their hands thoroughly.

• Small amounts of the chemicals were used and when unsure the TA was consulted.

• Waste was disposed of in the designated waste bins/containers at the end of the experiment.

• The SDS was also referred to for chemicals chosen and their safety was discussed among peers and TA.
Methods Part 2
0.002M* 0.005L= (.000001 mol Fe(NO3)3)/.01L)= .001M
Goumi G.
Kasi R.
Fiifi B.
Savannah E.

Tube 1: .002*.001L=(.000002KSCN/.01L)=.0002M
Tube 2: .002*.0015L=(.000003KSCN/.01L)=.0003M
Tube 3: .002*.002L=(.000004KSCN/.01L)=.0004M
Tube4: .002*.0025L=(.000005KSCN/.01L)=.0002M

Nitric Acid (HNO3):

Hazardous and highly corrosive mineral acid, avoid direct contact with skin and inhalation of its fumes. Wear proper PPE (MSDS).

Potassium Thiocyanate (KSCN):
It is very hazardous in the case of skin contact, eye contact, and ingestion. It is irritating to the skin and eyes, and toxic when ingested. Wear proper PPE.(MSDS).

Iron (III) Salts (Fe(NO3)3):
Hazardous in case of ingestion. No known effect on eye or skin contact, rinse with cold water for a few minutes. For precaution wear proper PPE. (MSDS).

First Aid Measures for all chemicals:

Immediately flush skin or eye(s) with cold water for at least 15 minutes. If inhaled, get fresh air. If not breathing, perform artificial respiration. If ingested seek medical attention. (MSDS).
Test tube 1
Results Part 1
Fe^3+ + SCN^--> Fe(SCN)^2+
Results Part 2
Keq= 422.69
Test Tube 2
Fe^3+ + SCN^--> Fe(SCN)^2+
Keq= 330.49

Test Tube 3
Fe^3+ + SCN^--> Fe(SCN)^2+
Keq= (9.63*10^-5)/(9.03*10^-4)(3.03*10^-4)
Keq= 351.96
Test Tube 4
Fe^3+ + SCN^- -> Fe(SCN)^2+
"Homeostasis is the ability of an organism to maintain equilibrium..." (Writer, L.G.). All organs in our body must maintain equilibrium in order to function properly. If equilibrium is not established, then there will be problems, health issues, or even organ malfunctions. For instance, the equilibrium of blood pressure must be sustained because if the pressures were imblanaced this can lead to either a high or low blood pressure. Having high or low blood pressure can lead to strokes, heart attacks, kindey failures, and many other damages. However, the body always finds a way to come back to equilibrium; in the example of when the blood pressure increasing drastically, releasing blood through the nose or the mouth may help the body stabilize and balance the blood pressure back to normal. According to Penn Medicine Research, metabolism balances homeostasis. This connects back to our lab because we do not realize how important homesostasis/equilibrium is in our day to day life. Changes in temperature would cause our body to immediately adjust to the temperature by creating a new equilibrium. Even in our previous lab dealing with kidney stones; a kidney stone forms when the bodily fluids lack substance to dilute the crystals found in the kidney. This would result in the increase of the concentration of the calcium ions causing an imbalance in the concentration of the calcium ions and the bodily fluids.
Keq= 1.3*10^-4/(8.7*10^-4)(3.7*10^-4)
Keq= 403.85
Average Keq
= 377.25
Percent error=( (experimental-theoretical)/theoretical)* 100
= ((377.25-138)/138)*100= 173.35%
Material Safety Data Sheet (MSDS) List https://www.sciencelab.com/msdsList.php (accessed April 4, 2017).
On the second week, it was decided that the fifth tube would not be taken into consideration since its value was too small and it did not make sense in the curve.
When comparing the Keq calculated to the theoretical Keq, there was a percent error of 173% which indicates that something went wrong.
Equilibrium in everyday life https://pakoraz.wordpress.com/2011/03/01/equilibrium-in-everyday-life/ (accessed Apr 8, 2017).

Writer, L. G. What Hormone is Responsible for Restoring Homeostasis? http://sciencing.com/hormone-responsible-restoring-homeostasis-13417.html (accessed Apr 8, 2017).

The objective of this lab was to determine the equilibrium constant of Fe(SCN)^2+ using spectroscopy and the concentrations that were calculated. Our hypothesis was supported because the value of absorbance increased proportionally creating a line with a psitive slope. As seen in our results, we had a very large percent error; however, this could have been caused by the errors we had during the lab. Some of the errors were, the faulty reading of the spectrophotometer, the type of test tube we had, and some of the test tubes being a little dirty. If this lab were to be repeated, some improvements to be made are having more trials with each test tube, using spectrophotometers that do work being constant in every reading, and making sure the test tubes are clean and of the same type/shape.
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