Takea Niragira Divora AsghedomArshdeep Sangha Chem 1420 Section 321 April 3

Takea Niragira
Divora AsghedomArshdeep Sangha
Chem 1420 Section 321
April 3, 2018
Experiment 22 Molar Solubility and Determination of Solubility Product
Purpose: Determine the solubility product for the dissociation of calcium hydroxide by measuring the concentration of the hydroxide ion in the saturated solution.
Data Table of Physical Constants:
Compound MW in g/molMP in º C BP in º C p in g/cm3 Hazards Disposal
Calcium Hydroxide 74.093 580º 2,850 º 2.21 Severe skin and eye irritant organic
Hydrochloric Acid 36.46 -26 º 110 º 1.18 Severe skin and eye irritant organic
Procedure:
Determination of The Solubility Product of Calcium Hydroxide Using PHydrion Paper
Pour approximately 80ml of saturated calcium hydroxide into a 100ml beaker. Dip the tip of small strip of pHydrion paper into the solution. Estimate the pH of the saturated, as best as you can, by comparing the tip of the strip to the color chart that is provided for you to use. Record the estimated pH on your lab data sheet. Now estimate the solubility product of calcium hydroxide using your estimated pH and equations 22.2 – 22.5. Remember Ca2+ = 0.5 OH-.

Determination of The Solubility Product of Calcium Hydroxide Using A Glass pH Electrode
Dilute the saturated calcium hydroxide solution with deionized water. Without disturbing the saturated calcium solution, transfer 5.0 ml of the saturated calcium hydroxide solution (by pipet) into a 250 ml beaker. Now add 95 ml of deionized water (graduated cylinder). Stir thoroughly to mix. Now measure the pH of the solution with the PASCO pH electrode.

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Calibrating the pH Electrode
Click on the Capstone icon
Obtain a wireless sensor, press the ON button to turn it on, a red light should begin to blink
Select “Hardware Setup” found in the tools palette
Select the Bluetooth # that matches the device ID #: red light should turn green
Click “Calibration”
Choose pH as the type of measurement to calibrate, click next
Choose “Two Standards (2 point)” as the type of calibration
Calibrate the first point
Fill a 50 ml beaker with about 40 ml of pH 4 standard
Immerse the probe into that solution, wait for the pH to equilibrate
Click “Set current value to standard value”
Calibrate the second point
Change the 7.00 value to 10.00 to calibrate pH to 10
Fill another 50 ml beaker with pH 10 buffer solution
Carefully, rinse the electrode with the squeeze bottle filled with DI water.

Blot the pH electrode dry with a clean paper towel
DO NOT BUMP THE ELECTRODE
Gently, immerse the probe into the pH 10 beaker solution and wait for pH to equilibrate
Click “Set current value to standard value”
After Equilibration
Click “Set current value to standard value.” Click next review your calibration and accept…Click on the digits display located on the digits palette and drag it into the home page. Click on the <Select a Measurement> and select pH. Record the pH on the lab sheet. Calculate H3O+ in the solution by substituting the measured value of pH into equation 22.3, which is the inserted into equation 22.5 to get OH- in the diluted solution. You will need to multiply the value by 20 to xsdr4 undo the dilution that was made when 5ml of saturated calcium hydroxide mas mixed with 95 ml of deionized water.
Pre-Lab Questions: None
Observations:
The pH paper was a dark blue around 13 which was much less than the literature value. We were unsure with the first titration, but our TA cleared up our confusion by confirming our methods were correct. The second titration went smoothly as it was similar to the first.

Results:
Solubility Product using pHydrion paper
Color of pHydrion strip: Dark Blue
pH of saturated solution based on color guide: 13
Hydronium ion concentration in saturated solution M: 1×10-13
Hydroxide ion concentration in saturated solution, M: 0.1
Estimated solubility product for calcium hydroxide: 5×10-4
Solubility Product Determination from pH Electrode Measurement
pH of diluted calcium hydroxide solution: 11.55
Hydronium ion concentration in diluted solution M: 2.8×10-12
Hydroxide ion concentration in diluted solution, M: 3.5×10-3
Hydroxide ion concentration in saturated solution, M: 0.071
Calculated solubility product of calcium hydroxide: 2.5×10-3
Literature value for solubility product of calcium hydroxide: 6.5×10-6
Molarity of hydrochloric acid, M
Initial burette reading before HCL addition, ml
Final burette reading after HCL addition, ml
Volume of hydrochloric acid used, ml
OH- in saturated Ca(OH)2 solution, M
Calculated solubility product from titration
Average value of solubility product from titration: 1.5×10-3
Literature value for solubility product of calcium hydroxide: 6.5×10-6
Trial 1 Trial 2
#12 0.02
0.02
#13 0 27.5
#14 27 70.5
#15 66 0.0564
#16 0.0528 0.0564
#17 1.4×10-3 1.6×10-3
Conclusions:
The objective of the experiment was to determine the solubility product of calcium hydroxide using pHydrion paper and titration. Our TA confirmed our results complied with average seen conclusions.

Post-Lab Questions: None