topic 4 block a
TRANSCRIPT
Group 4: Solubility
Block A
Carolina ZarateJason WangMichael Yeh
Introduction
TitleIntroduction
The ProblemBasic ResearchBalanced EquationPrevious ExperimentsWhy?Hypothesis
Stella ModelThe Solvation ProcessDeriving the EquationThe Dynamic ModelEvaluating the Model
ProcedureMaterialsMethods
Data AnalysisDataPHS Block A BoxplotsOverall BoxplotsGraph ComparisonAnalysisProblems EncounteredConclusion
Sources
The Problem
• General Question:What is the effect of temperature on solubility of salts?
• Tested Question:What is the effect of temperature on
the solubility of potassium nitrate at temperatures of 0oC, 25oC, and 60oC?
Introduction
Basic Research
Basic facts about Potassium nitrate, or KNO3
Potassium nitrate canbe dissolved in water
It is an orthorhombic crystal.
Its melting pointis 334oC
Its boiling pointis 400oC
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)
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
Introduction
Introduction
Why?
Real-world applications of the results gathered from our experiment include:
• Solutions in cooking and food
• Solutions found in living organisms
• Industry, such as ore processing
The solubility of potassium nitrate is expected to increase exponentially as temperature increases.
• Other solids soluble in water follow similar trends
• A dynamic model in was created in Stella and used to predict the solubility at each temperature
Introduction
Hypothesis
Stella Model
TitleIntroduction
The ProblemBasic ResearchBalanced EquationPrevious ExperimentsWhy?Hypothesis
Stella ModelThe Solvation ProcessDeriving the EquationThe Dynamic ModelEvaluating the Model
ProcedureMaterialsMethods
Data AnalysisDataPHS Block A BoxplotsOverall BoxplotsGraph ComparisonAnalysisProblems EncounteredConclusion
Sources
Stella Model
The Solvation Process
• When KNO3 and H2O form a solution, the KNO3 dissociates into K+ and NO3
- ions.
• At equilibrium, a pair of ions will recombine for each pair that disassociates
• The solubility product constant for our solution isKsp = [K+][NO3
-]
K+ NO3
-
K+ NO3
-
K+ NO3
-
K+ NO3
-
K+ NO3
-
K+ NO3
-
Dissolving potassium nitrate
Stella Model
Deriving the Equation
H: Enthalpy change
S: Entropy change
G: Free energy change
T: Temperature (Kelvin)
R = 8.314 J/(mol*K)
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))
ICE box: x is the solubility
Stella Model
Deriving the Equation
KNO3 K+ + NO3
-
# 0 0
-x +x +x
# - x x x
Ksp = [K+][NO3-] = x2
x2 = eS / R - H / (R * T)
x = Sqrt(eS / R - H / (R *
T))
Stella Model
The Dynamic Model
The values for S and H were found in The CRC Handbook of Physics and Chemistry
Stella Model
The Dynamic ModelPredictions:
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.
Stella Model
Evaluating the Model
Reasons for the linear solubility curve:
• Only one changing variable, T
• More accurate at lower temperatures
• To fix this, it would have been necessary to find the change in temperature
Procedure
TitleIntroduction
The ProblemBasic ResearchBalanced EquationPrevious ExperimentsWhy?Hypothesis
Stella ModelThe Solvation ProcessDeriving the EquationThe Dynamic ModelEvaluating the Model
ProcedureMaterialsMethods
Data AnalysisDataPHS Block A BoxplotsOverall BoxplotsGraph ComparisonAnalysisProblems EncounteredConclusion
Sources
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
Procedure
Methods
1. Measure 10 mL of tap water and pour into Erlenmeyer flask.
2. Put Erlenmeyer flask onto a hot plate and heat to 60oC. (Use GLX to measure temperature)
Procedure
Methods
3. Measure 6 g of potassium nitrate in a weighing boat on an analytical scale
4. Remove the Erlenmeyer flask from the hot plate
5. Pour the potassium nitrate and the magnetic stirrer into the Erlenmeyer flask
Procedure
Methods
6. Pay attention to the temperature as the KNO3 dissolves.
7. Allow the magnetic stirrer to run for 2-5 minutes
8. Remove the magnetic stirrer and temperature probe
Procedure
Methods
9. Place a filter paper into the funnel, and insert into the vacuum flask
10.Pour the contents of the Erlenmeyer flask through the filter paper
11.Remove the filter paper and place on the table to dry.
Procedure
Methods
12.Place an unused filter paper on the analytical scale and zero it
13.Place the dry paper with the potassium nitrate on the scale to weigh the undissolved solute
14.Subtract the weight from 6 g
Procedure
Methods
15.Repeat this process 4 more times
16.Repeat 1-15, but heat water to 25oC instead
17.Repeat 1-15, but use an ice bath to cool water to 0oC
Ice Bath
Drying KNO3
Data & Analysis
TitleIntroduction
The ProblemBasic ResearchBalanced EquationPrevious ExperimentsWhy?Hypothesis
Stella ModelThe Solvation ProcessDeriving the EquationThe Dynamic ModelEvaluating the Model
ProcedureMaterialsMethods
Data AnalysisDataPHS Block A BoxplotsOverall BoxplotsGraph ComparisonAnalysisProblems EncounteredConclusion
Sources
Data & Analysis
Data
Block Temp oC
Trial 1 Trial 2 Trial 3 Trial 4 Trial 5
PHS: A
0 19.4 15.8 15.8 13.8 16.7
25 23.5 23.4 23.1 22.5 22.8
60 40 38.1 41.2 43.3 42.3• We did 15 trials, 5 trials at each temperature
• We used 10 mL of water and 6 g of KNO3 per trial, but we scaled our results up to 100 mL and 60 g
Data & Analysis
DataBlock Temp oC Trial 1 Trial 2 Trial 3 Trial 4 Trial 5 Trial 6 Trial 7 Trial 8 Trial 9 Trial 10 Trial 11
PHS: A 0 19.4 15.8 15.8 13.8 16.7 * * * * * *
25 23.5 23.4 23.1 22.5 22.8 * * * * * *
60 40 38.1 41.2 43.3 42.3 * * * * * *
PHS: B 0 15.00 13.40 11.60 12.10 11.25 * * * * * *
25 36.70 37.35 39.25 36.95 42.15 37.95 * * * * *
60 81.85 98.50 100.50 109.75 97.00 102.85 * * * * *
MBHS: A 0 17.00 9.86 25.20 10.24 9.74 10.28 12.58 6.64 13.06 8.62 *
25 32.30 30.76 33.24 35.12 39.38 35.36 44.00 45.00 34.82 33.50 *
60 64.02 46.44 42.22 80.80 49.80 99.04 70.70 64.40 * * *
MBHS: B 0 2.40 10.90 15.76 12.20 5.25 11.50 18.66 17.00 5.40 13.91 16.23
25 13.23 26.31 34.84 32.31 31.79 34.90 39.30 31.93 37.55 33.12 22.30
60 114.36 117.67 97.32 111.20 36.19 76.96 44.20 24.72 71.84 35.26 35.66
MBHS: C 0 13.80 13.00 14.00 13.00 11.50 12.50 11.00 13.50 14.50 9.50 *
25 26.00 26.50 26.00 29.50 25.40 28.00 29.25 25.20 29.10 26.80 *
60 42.90 64.50 109.95 75.00 61.00 54.00 66.00 64.00 74.50 58.50 *
MBHS: D 0 12.50 14.10 14.20 13.60 13.90 12.80 15.40 13.20 16.80 15.00 15.20
25 42.80 38.50 33.94 33.10 36.40 41.60 39.80 45.20 41.00 38.40 40.60
60 120.30 114.40 110.00 110.00 113.00 123.00 110.00 120.00 103.00 106.00 *
PHS Block A Boxplots0°CMedian: 15.8Minimum: 13.8Maximum: 19.4Interquartile 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
Data & Analysis
Overall Boxplots0°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
Data & Analysis
Graph ComparisonData & Analysis
• Our data graph intersects overall data graph
• Large difference in 60°C data
AnalysisData & Analysis
• Our low IQRs mean the data is very precise
• Mean and median are fairly close, meaning data is consistent
• Data did increase exponentially, but not exactly as predicted
• 0oC trials dissolved more than expected; room temperature heated the solution
• 60oC dissolved less than expected; room temperature cooled the solution
AnalysisData & Analysis
• Overall results closely match results from professional experiments
• Lots of inconsistencies shown in the boxplots
• Much larger IQR for 60oC than our block alone
• More outliers for 0oC: 6 as opposed to 1 and none
• Variations in data due to different procedures
• Even with larger IQRs and more outliers, mean and medians of the 155 trials match our hypothesis closely
Problems EncounteredData & Analysis
• Maintaining temperature: cooling to 0o and heating to 60oC
• Rate of dissolution: used a magnetic stirrer to accelerate process
• Transferring solution: wet residue stuck to sides of flask, used spatula to remove it
• Measuring remnants: wet filter paper was inconsistent, waited for the crystals to dry
ConclusionData & Analysis
Hypothesis confirmed: the solubility did increase exponentially when the temperature increased.
• 155 trials not enough to definitively answer the question – it does provide solid evidence
• In the future, more data can be collected using same methods
• Possible variations:• Change temperatures tested• Use different salts instead of KNO3
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Any Questions?