CHEM123L Study Guide - Final Guide: Magnetic Stirrer, Purified Water, Ph Meter

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blueduck407

18 Mar 2014

School

University of Waterloo

Department

Chemistry

Course

CHEM123L

Professor

Carey Bissonnette

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Document Summary

Experiment procedure summary 4: ph chemistry: acid base titrations and buffers: sign out from storeroom, 1 50 ml pipette bulb, 1 50 ml burette, 1 magnetic stirring bar, 1 25 ml pipette. Make sure that your ph meter has been calibrated. The ph meter should be turned on and the numbers 7 and 4 should be showing. Part a: titrations of a weak acid with strong base. Pipette 25 ml of 0. 1 m acetic acid into a clean 400 ml beaker by placing the magnetic bar first. Copy the exact molarity given on the stock bottle. Add 150 ml deionized water and 2 drops of phenolphthalein. Obtain 60 ml of the unknown naoh solution and prepare for titration. Place it in position to titrate to ch3cooh solution. Record the burette readings and ph, both to two decimals place. Part b: titrations of a weak base with a strong acid. Pipette 25 ml of 0. 1m ammonia into a clean 400 ml.

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PROCEDURE Safety Precautions: Sodium hydroxide and Acids are corros and will damage your skin and eyes. To perform the experiment, a pH sensor will be placed in the acid solution. The pH sensor is used to monitor pH as the titration with sodium hydroxide is performed Record the pH values and corresponding volume (mL) of NaOH added. Enough data points will have to be generated to obtain a smooth curve. In some regions of the titration, the pH will change very slowly, and larger increments of base, mL, can be added. Near the equivalence point (before and after), the pH changes very quickly, and the NaOH should be added dropwise. The subsequent pH reading should be recorded after the addition of each quantity of NaOH. The titration setup is shown in Figure 3. Center the beaker and the stir-bar on the stir-plate. Clamp the pH probe such that the tip and ball are submerged below the surface of the solution but, not touching the bottom. Allow sufficient clearance to allow the stir bar to spin freely 1. 150 mL beakers can be used to transport reagents from standardized bottles. This will avoid cross- contamination of the standardized bottles Obtain approximately 15 mL of the standardized hydrochloric acid, solution, approximately 15 mL of the standardized acetic acid solution, and approximately 75 mL of the standardized sodium hydroxide solution in separate beakers. Use the lab tape and markers to label beakers. Beakers should be covered with a watch glass when they're not in use 2. Record the concentrations of the HCI, CH3COOH, and NaOH solutions, which are on the reagent bottles, in the laboratory notebook. 3. Obtain a magnetic stir plate and a ring stand with a burette clamp and a small 3-finger clamp Figure 3. Titration setup 4. Clean and rinse a 25 mL burette. This burette will be used to dispense the NaOH. The lab team should discuss and decide on the appropriate material to use for the final rinse. If air bubbles appear in the tip of the burette, aggressively tap the burette to dislodge the bubbles. If bubbles continuously reappear then the burette has a small leak and the valves need to be serviced (discuss this with the lab instructor). TITRATION OF HCL 5. Measure 100.0 mL of DI water with a 100.0 mL graduated cylinder and pour it into a 250 mL beaker. Use a pipette to add 10.00 mL of the standardized acid solution into the same 250 mL beaker and add 2-3 drops of phenolphthalein indicator. Place the Teflon Stir Bar in the beaker carefully. General Chemistry 2

PROCEDURES :

Rinse and flush a burette with the solution of NaOH provided and set it up. Fill the burette with the solution of NaOH solution.

Using a 15-mL volumetric pipette, collect an accurate volume of the 0.1 M HC1 solution and add it to a 250-mL beaker that contains about 50-mL of deionized water and a magnetic stir bar. Place the beaker on a stir plate and begin stirring.

Turn on the Vernier LabQuest by pressing the silver power button in the upper left corner. Connect a pH probe into the slot marked CH 1, this slot is located on the top edge of the LabQuest. The LabQuest will automatically recognize the type of probe and begin to display the pH data.

Using the stylus provided tap the tabs displayed at the top of the screen to toggle between the Meter screen, Graph screen and Data Table screen.

Conduct the titration by adding the basic solution from the burette to the acid solution. You should take the pH reading after every addition of I.00 mL of the base solution. Continue the titration process until you have added 30.00 mL of the base solution.

Rinse the probe several times with tap water followed with deionized water.

Insert the clean probe you just rinsed in the acid solution labelled X and determine its pH.

Insert the clean probe you just rinsed in the base solution labelled Y and determine its pH.

Dispose the waste according in the labeled waste disposal container.

graph of pH vs. volume of NaOH solution added that will be graded according to the graph guidelines provided below;

GRAPH GUIDELINES

Submit a FULL PAGE OF titration curve by stapling it to this report sheet. Your graph will be graded based on the âChemistry Graph Checklistâ posted on Blackboard, which includes overall appearance. You may seek out help from peers while learning to use Excel, but your graph must be your own.

1. Appropriate tittle (5 points)

2. Correct labelling of both axes (10 points)

3. Correct units on both axes (10 points)

4. Graph occupying at least Â¾ of the page used (5 points)

5. Correct scales for both axes (10 points)

6. General shape of the graph (10 points)

Please someone helps me I did it but i dont know what im missing

can someone complate what I miss

CHEM123L Study Guide - Final Guide: Magnetic Stirrer, Purified Water, Ph Meter

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