Lab 8 CHM - lab report PDF

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Gianina Favata 10-24-20 CHM 124 Pre- lab 8 Title: introduction to Acid- Base Titration

Objective: The objective of this part of the experiment is to test the accuracy and precision of 5.00mL volumetric pipette. Hypothesis: the volume of the volumetric pipette is 5.00mL. The mass of 5.00mL of water will be measured in each trial. Then the mass will be converted to volume. To do this conversion the property of density will be used, as it is an intensive property. Variables: Independent variable(s): the mass of water Dependent Variable(s): the volume of water

Procedure part 1 : 1. 2. 3. 4. 5. 6.

Gather all the materials need for the experiment. Get the mass of a clean and dry 50mL Erlenmeyer flask Using a volumetric pipette and pipette pump, put 5.0mL of water into the flask. Get the new mass of the flask with water Find the mass of water from the difference. Repeat these steps four more times to determine the accuracy and precision of the volumetric pipette.

Part 2:

Objective : The objective of this part of the experiment is to titrate 5.00mL of dilute acid with 0.001 M of NaOH solution, this will be done four times, to test the precision and accuracy.

Hypothesis : The concentration of the hydrochloric acid will be 0.200M. to determine the actual concentration an acid- base titration will be done. The concentration of the NaOH will be known before the start if this experiment. The chemical phenolphthalein will been used to monitor the

reaction. The Phenolphthalein is clear when it is in an acid solution, when it becomes a more basic solution the phenolphthalein turns pink.

Vraiables: Independent Variable(s): is the volume NaOH.

Dependent Variable(s): concentration of HCl . Procedure: 1. Gather all the necessary materials for this part of the experiment. 2. Using the 5.00 M NaOH solution given to do so, ass 2.0 mL of it to a 100mL volumetric flask and fill up to the calibration line with water and mix it, this will make 100mL of the 0.100 M NaOH. 3. To make the hydrochloric acid solution add approximately 3.5mL of 3.00 M of the hydrochloric acid into the 125 mL Erlenmeyer flask, fill it up to the 50mL with water. 4. Using the volumetric pipette, transfer 5.00mL of diluted hydrochloric solution to a clean Erlenmeyer flask, use water to clean the sideas of the flask of any left over solution, this step should be setup four times for four trials. 5. Add one or two drops of the phenolphthalein to the flask 6. Before beginning the titration the burette must be cleaned and the proper materials must be obtained. 7. Get three beakers and label them accordingly, one is for the waste, one is for the NaOH solution and one is for the water. 8. To clean the burette. In three portions, add about 5mL of water into it and drain it into the waste beaker. 9. Add about 1-2 mL of the NaOH solution into the NaOH beaker and then pour it into the burette, in three portions and let it drain out into the waste container. 10. Once the burette us cleaned fill it with the NaOH solution, make sure there is no air bubbles at the bottom and record the volume. 11. Slowly add the NaOH solution from the burette into the flask with the HCl solution until the indicator starts to turn pink, be sure to swirl when titrating it to ensure the NaOH is dissolving. 12. Recording the final volume of the burette, find the volume of the NaOH solution add by finding the difference between the beginning and the final volume of the burette. 13. Repeat this for four trials. Chemical Hazards and Waste

Gloves, goggles and lab coat must be worn at all times. 5M sodium hydroxide and 3M HCl are hazardous, toxic and corrosive, handle with care. All glassware must be cleaned before using them in the titrations. Sodium hydroxide solutions will leave a corrosive residue behind, make sure all glassware is rinsed after it is used. All waste should be mixed and then poured down the drain as described.

Conclusions: Part 1 The results supported the hypothesis, the reason is the average volume transferred by the pipette was 5.00mL. The statistical calculations that help to support this hypothesis were that the percent error was 0.11% , the RSD was 2.59 and the standard deviation was 0.002598. The pipette was accurate and the reason why it was accurate was the calculation of percent error was only 0.11% it was less than one percent. The pipette was precise for the mere fact that the average volume of water it can hold was 5.00 mL.

Parts 2. The data and results supported the hypothesis. The average concentration of the hydrochloric acid was 0.2M. The RSD of the measurements was 16.29 ppt. The standard deviation was 0.000868. The measurements were precise for the fact that the average molarity was 0.21M. Yes, the accuracy of this experiment was able to be determined seeing as the results supported the hypothesis’s and that they were proven....