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# QCC CHM 124 - Determination of an Equilibrium Constant

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Alferid Hussin ShifaCHM (Course 124) (Section 01)Lab (5) Oct 10/2019Lab 5: Determination of an Equilibrium ConstantObjective: The purpose of this experiment is to study factors which can disturb an equilibrium system. Specifically, Calculate the Equilibrium Constant of 2+¿−¿´← FeSCN¿3+¿+SC N¿Fe¿ List of chemicals, & hazard:- Iron(III) nitrate - Fe(NO3)3 (highly hazards)- Nitric acid - HNO3List of Chemicals with Safety Hazard: There are Hazards chemicals in this experiment.I. Safety Precautions:- Be cation when handling the solutionII. Handling Equipment:- Be careful when handling the spectrophotometerIII. Waste Disposal:- Disposal the mixtures in the sink, or into the appropriate waste beaker.List of Equipment:Flask Pipet aid & disposable pipet’s (Three of 10 mL)Beaker Parafilm Distilled water Test TubesSpectrophotometer Pre-Lab Questions:1.12+¿Fe(SCN )¿¿3+¿Fe¿¿−¿S CN¿¿¿¿¿Procedure in short: 1. Set up 5 test tubes with 5ml of Fe(NO3)3. Add 1ml of KSCN to Tube 1, 2ml to Tube 2, 3ml to Tube 3, 4ml to Tube 4, and 5ml to Tube 5. 2. Tube 1 will get 4ml of water, Tube 2 gets 3ml, Tube 3 gets 2ml, Tube 4 gets 1 ml, and Tube 5 does not get any distilled water. 3. Add exact 2 mL of 3 HCl. slowly into the mixture in the Erlenmeyer flask. As you add the HCl, swirl the mixture. Finale result should have a dark yellow solution.4. Once everything is inside, we cover the top of the tube with parafilm paper. Invert the tube so the solution touches the parafilm paper. 5. Put the parafilm paper in the spectrophotometer to measure the absorbance. From this point, the equilibrium constant can be calculated 6. Repeat this process if needed.ResultTable 12Test Tube Volume of concentrated 0.2M Fe(NO3)3 in 1M HNO3 (ml)Volume of 2 * 10^-3M KSCN (ml)Volume of purified water (ml)Absorbance1-1 5 0.5 4.5 0.4511-2 5 1.0 4.0 0.8851-3 5 1.5 3.5 1.337Table 2Test Tube Volume of concentrated 0.2M Fe(NO3)3 in 1M HNO3 (ml)Volume of 2 * 10^-3M KSCN (ml)Volume of purified water (ml)Absorbance2-1 5 1.0 4.0 0.1112-2 5 2.0 3.0 0.2092-3 5 3.0 2.0 0.3252-4 5 4.0 1.0 0.4342-5 5 5.0 0 0.539Table (calculation)Test Tube Absorbance FeSCN2 ion concentration (moles)1-1 0.4511.0*1 0−62-2 0.8852.0*1 0−62-3 1.3373.0*1 0−6None 0030.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.600.00E+005.00E-071.00E-061.50E-062.00E-062.50E-063.00E-063.50E-06f(x) = 0x − 0 Absorbance vs Concetration Absorbance(AU)FeSCN2 ion concentration (moles)Test Tube Kc Value2-1 1.25232-2 1.18572-3 1.23242-4 1.23592-5 1.2289Average Kc = 1.23Any specific observations:- The absorbance measured by the Spectrophotometer, get a higher measurement when the solution is darker.Conclusion:- The overall purpose of the lab was to use a spectrophotometer to determine the equilibrium constant of a chemical system and determine the equilibrium constant for 4a soluble equilibrium. Through the experiment, the data shows that as concentration of the solute Fe(NCS)2+ increases, the absorbance will also increase. Which absorbance values increase consistently throughout the trials, so this shows that the data was accurate. The overall average Kc was found to be

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