1. Group 4: Solubility Block A Carolina Zarate Jason Wang Michael Yeh

2. Title Introduction The Problem Basic Research Balanced Equation Previous Experiments Why? Hypothesis Stella Model The Solvation Process Deriving the Equation The Dynamic Model Evaluating the Model Procedure Materials Methods Data Analysis Data PHS Block A Boxplots Overall Boxplots Graph Comparison Analysis Problems Encountered Conclusion Sources Introduction

4. Introduction Basic Research Basic facts about Potassium nitrate, or KNO3 Potassium nitrate can be dissolved in water It is an orthorhombic crystal. Its melting point is 334oC Its boiling point is 400oC

5. Introduction Balanced Equation The equation for our experiment: KNO3(s) + H2O(l) ->K+(aq) + NO3-(aq) + H2O(l) The net ionic equation simplifies to: KNO3 (s) ->K+ (aq) + NO3- (aq)

6. Introduction Previous Experiments Our research found sources created by other scientists working in this field: Empirical data found in other researchers’ previous experiments The data showed an exponential increase in solubility with temperature

8. Solutions found in living organisms

12. At equilibrium, a pair of ions will recombine for each pair that disassociates

13. The solubility product constant for our solution isKsp= [K+][NO3-] NO3- NO3- NO3- NO3- NO3- NO3- K+ K+ K+ K+ K+ K+ Dissolving potassium nitrate

14. Stella Model Deriving the Equation Gibbs-Helmholtz Equation: G = H - T * S Relationship between Ksp and G: G = -R * T * ln(Ksp) H - T * S = -R * T * ln(Ksp) ln(Ksp) = (H - T * S) / (-R * T) Ksp = e(S / R -H / (R * T)) H: Enthalpy change S: Entropy change G: Free energy change T: Temperature (Kelvin) R = 8.314 J/(mol*K)

15. Stella Model Deriving the Equation Ksp= [K+][NO3-] = x2 x2 = eS / R - H / (R * T) x = Sqrt(eS / R - H / (R * T)) ICE box: x is the solubility

16. Stella Model The Dynamic Model The values for S and H were found in The CRC Handbook of Physics and Chemistry

17. Stella Model The Dynamic Model Predictions: 0°C:13 g KNO3 per 100 mL H2O. 25°C: 37.5 g KNO3 per 100 mL H2O. 60°C: 71.73 g KNO3 per 100 mL H2O.

19. More accurate at lower temperatures

21. Procedure Materials 1 PASCO Explorer GLX (#4) 1 GLX Temp Probe (Stainless Steel Chemical Resistant) 20 Weighing Boats 1 Analytical Scale 1 Glass Funnel 1 1000 mL Beaker 1 10 mL Graduated Cylinder 1 Vacuum Flask 4 50 mL Erlenmeyer Flasks 1 Hot Plate 1 Mixer (Separate from hot plate) 10 mL Tap Water (H2O) per Trial 6 g KNO3 per Trial Ice: enough to fill a 1000 mL Beaker 1 Plastic Pipette 15 Filter Papers 1 Small Magnetic Stirrer Pill 1 Magnet to take out the Pill

22. Procedure Methods Measure 10 mL of tap water and pour into Erlenmeyer flask. Put Erlenmeyer flask onto a hot plate and heat to 60oC. (Use GLX to measure temperature)

23. Procedure Methods Measure 6 g of potassium nitrate in a weighing boat on an analytical scale Remove the Erlenmeyer flask from the hot plate Pour the potassium nitrate and the magnetic stirrer into the Erlenmeyer flask

24. Procedure Methods Pay attention to the temperature as the KNO3 dissolves. Allow the magnetic stirrer to run for 2-5 minutes Remove the magnetic stirrer and temperature probe

25. Procedure Methods Place a filter paper into the funnel, and insert into the vacuum flask Pour the contents of the Erlenmeyer flask through the filter paper Remove the filter paper and place on the table to dry.

26. Procedure Methods Place an unused filter paper on the analytical scale and zero it Place the dry paper with the potassium nitrate on the scale to weigh the undissolved solute Subtract the weight from 6 g

27. Procedure Methods Repeat this process 4 more times Repeat 1-15, but heat water to 25oC instead Repeat 1-15, but use an ice bath to cool water to 0oC Drying KNO3 Ice Bath

28. Title Introduction The Problem Basic Research Balanced Equation Previous Experiments Why? Hypothesis Stella Model The Solvation Process Deriving the Equation The Dynamic Model Evaluating the Model Procedure Materials Methods Data Analysis Data PHS Block A Boxplots Overall Boxplots Graph Comparison Analysis Problems Encountered Conclusion Sources Data & Analysis

31. Data & Analysis PHS Block A Boxplots 0°C Median: 15.8 Minimum: 13.8 Maximum: 19.4 Interquartile Range: 3.25 25°CMedian: 23.1Minimum: 22.5Maximum: 23.5Interquartile Range: 0.8 60°CMedian: 41.2Minimum: 38.1Maximum: 43.3Interquartile Range: 3.75

32. Data & Analysis Overall Boxplots 0°CMedian: 13.3Minimum: 2.40Maximum: 25.20Interquartile Range: 3.8375Outliers: 2.40 5.25 5.40 6.64 25.20 19.4 25°CMedian: 33.50Minimum: 13.23Maximum: 45.20Interquartile Range: 11.8Outlier: 13.23 60°CMedian: 74.75Minimum: 24.72Maximum: 123.00Interquartile Range: 63.92Outliers: none

35. Mean and median are fairly close, meaning data is consistent

36. Data did increase exponentially, but not exactly as predicted

37. 0oC trials dissolved more than expected; room temperature heated the solution

39. Lots of inconsistencies shown in the boxplots

40. Much larger IQR for 60oC than our block alone

41. More outliers for 0oC: 6 as opposed to 1 and none

42. Variations in data due to different procedures

44. Rate of dissolution: used a magnetic stirrer to accelerate process

45. Transferring solution: wet residue stuck to sides of flask, used spatula to remove it

47. In the future, more data can be collected using same methods

48. Possible variations:

49. Change temperatures tested

51. Any Questions?