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Titration Lab chem 113...

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Ava Cherry TA: Hayley Nathaniel Secon: P6 Conductimetric Titration & Gravimetric Determination of BaSO4 Lab Report 1. Introduction: Conductimetric titration involves monitoring the conductivity during a reaction between sulfuric acid and barium hydroxide to determine the equivalence point. Based on the data observed and obtained during the reaction, one can find the concentration of the barium hydroxide solution. The reaction between the two leads to an insoluble product and water - the insoluble product being barium sulfate. The total number of dissociated ions within the solution is reduced dramatically during the reaction as a precipitate is created. Changes within the conductivity are monitored using a Conductivity Probe while sulfuric acid is slowly added to the barium hydroxide. While the reaction progresses, solid barium sulfate will precipitate from the solution. Weighing the salt will allow you to determine the concentration. Gravimetric analysis is a technique through which the quantity of the analyzed ion is determined through the measurement of mass. Gravimetric analyses depend on comparing the masses of two compounds containing the analyte. The principle behind quantitative analysis is that the mass of an ion in a pure compound can be determined then used to find the mass percent of an equivalent ion in a known quantity of an impure compound. so as for the analysis to be accurate, certain conditions must be met: ● The ion being analyzed must be completely precipitated. ● The precipitate must be a pure compound. ● The precipitate must be easily filtered 2. Procedure: 1. Obtain 10mL of the barium hydroxide solution and add 30mL of distilled water. 2. Connect the drop counter and the conductivity sensor. 3. Start the Logger Pro program and open the assignment file. 4. Obtain 60mL of sulfuric acid and record the precise concentration. 5. Calibrate the drop counter 6. Fill the reagent reservoir with 40mL of sulfuric acid. 7. Assemble the conductivity sensor and drop counter and add the magnetic stirrer. 8. Turn on the stirrer. 9. Conduct the titration. 10. Observe the graph and determine the equivalence point. 11. Place the beaker with the titrated solution on a hot plate and bring to a near-boil. 12. Weigh the filter crucible and place it in the vacuum titration apparatus. 13. Allow the solution to cool after being at a near-boil for a minute. 14. Wet the filter disk in the crucible with methanol then turn on the vacuum. 15. Quickly stir the solution and immediately begin filtering all of it into the crucible vacuum. 16. Put your crucible in the drying oven for 15-20 minutes. 17. Let the crucible cool.

18. Once cool, record the weight and determine the weight of barium sulfate collected. 19. Calculate the original concentration of the barium hydroxide solution. 3. Equations: V ×C=V ×C Molarity=mol of solute/ L of solution mol (Ba(OH)2)=mol (Ba SO4) mgBa SO4(1 mol Ba SO4/233 g) 4. Observation/ Data Equivalence Point from Titration: 19.460mL Molarity of sulfuric acid solution: .100 M Moles of barium from Titration:1.95 ×10−3 mol Volume of original barium hydroxide solution: 5.60mL Concentration of barium hydroxide from titration: 0.348M Mass of Crucible and precipitate: 33.499g Mass of Crucible: 33.024g Mass of Precipitate: 0.475g Concentration of barium hydroxide from gravimetric: 0.364M 5. Calculations (.100 mol H2SO41/ L of solution)×(.019460 L)=1.95× 10−3mol H2SO4=1.95× 10−3 mol Ba Molarity=mol of solute / L of solution 0.475g Ba SO4×(1mol Ba SO4/233g Ba SO4)=2.039 ×10−3moles BaSO4=2.039× 10−3 moles Ba 6. Discussion and Conclusion: Both techniques involved thorough computations and data collection. The slightest error in either technique would likely result in a far from accurate concentration of barium hydroxide. The concentrations of barium hydroxide obtained from both techniques were fairly precise but may not be accurate. As I am not sure what the actual concentration of barium hydroxide is, it is impossible to calculate the percentage error. However, the variation between the two results is only .024 so the precision is very good. The final concentration was between 0.348M and .364M. I feel the experiment was successful, especially in gaining experience in using those techniques as well as in operating the equipment involved. With such a lengthy and detailed experiment, there is more room for error. Errors could absolutely have arisen within the calculations, particularly in the conversions. Errors could also have arisen in the experiment itself in any of the following steps: calibration of the drop counter, flocculation of the solution, and having the solution reach boiling point or room temperature. I feel that if I had made any errors, it likely would have been within the calculations and conversions as it can be confusing going from one unit of measurement to another....