1. I-Acids and Bases Prem Sattsangi Copyright 2008

2. #2 Introduction to Acids and Bases Chapter - 8 Individual work Section A Facts and Questions. Section C Acid-base titration. M of Unknown HCl U.K.#_____. Section D Calibration of microburet. Section E Analysis of the egg shell.

3. #3 Getting Ready Waste Beaker 50 mL. 24 well tray with solutions. 12 well tray Microstirrer Distilled water bottle.

4. #4 Stock Solutions 2.00M HCl0.1M NaOH 0.10M HCl~1M NaOH BTB Crushed Egg shell 95% Ethanol

5. #5 Acid-Base Titration Equivalence point = The first blue well Add 1 drop NaOH to well #1, stir, wipe the stirrer clean… SERIAL TITRATION: #Drs NaOH = well# ColorY Y B B 0.1M NaOH1 2 3 4 5 6 7 8 9 10 11 12 0.1M HCl5 5 5 5 5 5 5 5 5 5 5 5 BTB1 1 1 1 1 1 1 1 1 1 1 1 Well#1 2 3 4 5 6 7 8 9 10 11 12

6. #6 Serial titration 0.1 M HCl Steps 43214321

7. #7 Calculation (drs. In place of mL) NaOH(aq) + HCl(aq)  NaCl(aq) + H 2 O(l) ______ drops X 0.1 M NaOH = 5 Drops X 0.1 M HCl Discuss with teacher if: Your end point is not in the fifth well.

8. #8 Calibration of the Micropipet [Uniform Size Drops] Fill MP with DW, Hold vertical ~1” from the tray. Squeeze gently 1 drop. Record weight up to 0.0000g. Tare the balance. Repeat, record 10 readings. Discard the readings that are too much off. You MUST have 10 good readings.

9. #9 Calculation of Mean and Standard Deviation Use TI 30 to calculate Mean and Std. Dev. E.g. if the date is 9, 4, 4, 5, Mean = 5.5Std. Dev. = 2.38…. Enter the data as follows. 9,  +, 4,  +, 4,  +, 5,  +, Mean: 2 nd  xn-1 = 2.38; Std.D. 2 nd X(bar) Write ST.#, Wt of 1 drop (g) on the pipet. Apply a tape over it.

10. #10 Getting Ready for U.K. U.K.#___ Check. It should correspond to your station #. M ranges from 0.2 to 0.4 M. 12 well tray 2 drs U.K. + 1 dr BTB 24 well tray 20 drs U.K. + 2 drs BTB

11. #11 Titration of U.K. Empty the U.K. micropipet in its well. Wash 2-3 times with DW. Rinse 2-3 times with 0.1 M NaOH. Fill ~half way with 0.1 M NaOH. Titrate: Keep micro stirrer in tray till the end point is reached.

12. #12 Weighing of the Egg Shell (Balance drifts) Check balance reading, 0.0000 TARE if needed Weigh a plastic tray on Analytical balance. Add slightly less than a level spoon. (~0.05 g egg shell) Record weight up to 4 decimal places.

13. #13 Weighing Observations OBSERVATIONS: Weight Wt of Plastic Tray = 0.5153g Wt of Tray + egg shell = *1 0.5646 After transfer Weight of empty tray. = *0.5161g Egg shell wt. = *1 0.5646 - *0.5161 Difference in weights: = 0.0485g

14. #14 Reaction: Egg shell + HCl Running the reaction: CaCO 3 + 2HCl  CaCl 2 + H 2 O + CO 2 [1 mol CaCO 3 reacts with 2 mol HCl] Add 1-2 drops of 95% ethanol to egg shell. Use calibrated micropipet to add 30 drs of 2.00 M HCl in the well with egg shell.

15. #15 Caution: Hot Water Hold pipet with a folded paper towel. Take ~1 cm hot water 2-3 times to condition the glass pipet. Add hot water in adjoining well. Leave a microstirrer in the well and stir every other minute. Allow the reaction to proceed (~10-15 minutes).

16. #16. Result Reporting Molar concentration of NaOH is to be copied from the Board. Calculate the result carefully. Check before submitting.