Chem 162 lab report or formal lab PDF

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FINAL LAB REPORT...

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EXPERIMENT: CHEMICAL KINETICS: THE RATE OF A CHEMICAL REACTION USING AN IODINE CLOCK REACTION.

OBJECTIVE : In this lab, the rate of the reaction of ammonium persulfate, (NH4)2S2O3, with potassium iodide, KI will be studied. One of the purposes of this experiment is to determine rate law. **Safety goggles and other safety procedures must be followed for this lab** Purpose: In this experiment we will be given a solution of sodium hydroxide of known concentration which we will use to determine the equivalent mass of an unknown organic acid. PROCEDURE: PART A: Three room temperature runs. -

Record the temperature of the laboratory in the notebook.

-Obtain two clean and dry plastic test tubes with screw caps, labeled A and B. -

Add from burets the indicated volume of each solution to test tube (A) and test tube (B).

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Before mixing the contents of the test tubes, make sure you know how to use the timer properly.

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The contents of test of test B containing (NH4)2S2O8(aq) and starch will be added rapidly by one student of the pair to the contents of test tube A. The second student of the pair will start the timer at the exact time when the transfer begins.

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As soon as the transfer is complete, the first student will cap test tube A and invert the test tube rapidly about 15 times while shaking it simultaneously to insure mixing.

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After mixing, the test tube should be placed in a dry beaker to guard against accidentally warming of the contents through contact with your hands.

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The second student of the pair will stop the timer at the exact time at which a dark color appears.

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Each experiment should be performed in duplicate.

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Before performing the second run, discard the contents of the test tubes in the white waste buckets in your hood.

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Wash the test tubes at the sink and then rinse with distilled water.

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Dry the inside with a paper towel.

PART B: High Temperature Run (Fourth Experiment) -

Record the temperature of t The laboratory in your notebook.

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Obtain two clean and dry plastic test tubes with screw caps, labeled A and B.

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Add from burets the indicated volume of each solution to test tube (A) and test tube (B).

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As soon as the transfer is complete, the first student will cap test tube A and invert the test tube rapidly about 15 times while shaking it simultaneously to insure mixing.

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One student of the pair removes both test tubes from the water bath and carefully, btu quickly pours the contents of test tube B into the contents of test tube A.

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The second student of the pairs starts the timer when the transfer begins. The first student then caps test tube A and inverts the test tube rapidly about 15 times while shaking it simultaneously to insure mixing.

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Test tube A is then returned to the water bath to insure the temperature of the reacting system remains at the previously recorded temperature.

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The second student of the pairs stops the timer the exact time at which the dark color appears.

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Record the time contents of the table on the board.

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Before performing the second run, discard the contents of the test tube in the white waste buckets in your hood.

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Wash the test tubes at the sink and then rinse with distilled water.

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Dry the insides with a paper towel.

PART C: Room Temperature run with catalyst ( Fifth experiment ) -

Clean and dry the test tubes.

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Add from burets the indicated volume of each solution to test tube (A) and test tube (B).

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Add 1 drop of 0.20 M Cu(NO2)2(aq) to test tube A and shake gently.

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The first student of the pair then transfers the contents of the test tube A and the second student starts the timer as soon as transfer begins.

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The first student swirls the contents of test tube A without capping the test tube to insure mixing.

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The second student of the pair stops the timer at the exact time at which a dark color appears.

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Both students must be especially alert because the color change occurs almost at the instant the solutions from the two test tubes are mixed.

SOLUTIONS:

1.) Trail 1

Trial 2

Trial 3

Mass of unknown acid (g)

0.581g

0.586g

0.590g

Final Buret Reading (ml)

27.8ml

28.2ml

28.6ml

nitial Buret Reading (ml)

0.00ml

.1ml

.2ml

27.8ml

26.1ml

28.4ml

Volume delivered (ml)

2.) Show the calculation for the # moles of OH- used. .0278 x .1 NaOH = .00278 mol NaOH = Moles OH

+

3.) What are the # moles of H reacted Moles OH = H

+

4.) What are the # of equivalents of H titrated # of eq of H = # of mole of H since 1 : 1 acid/base rxn .281/.00278= 101.1 5.) Show the calculations of the equivalent mass of your unknown acid using Trial 1 in the table below.

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+

=

Trial

# moles of OH

1

.00278

.00278

.00278

207.7

2

.00281

.00281

.00281

207.7

3

.00284

.00284

.00284

207.7

# moles of H

# equivalents H

Equivalent Mass (g/eq)

6.) Show the Q test calculations for the most deviant value of the EM. Trial 1 Trial 2 Trial 3 0.581 / 0.00278 = 208.9 0.586 / 0.00278 = 208.5 0.590 / 0.00284 = 207.7

7.) Based on your Q-test results, show the calculations of the average equivalent mass for the remaining acceptable EM trials. 625.1 / 3 = 208.4 8.) Show the calculations of the average, variance, standard deviation, and

standard error of your “good” trials and use the SE to round the average. Variance = 0.375 Standard deviation = 0.612 Standard error = 0.353 9.) Identify your acid (include unknown letter) and calculate its MW from your average EM Potassium Hydrogen Phythalic 10.) Calculate the % error in your MW value:

204.2 - 208.4 / 204.2 x 100 = 2.06% 11.) Write the balanced equation for the reaction which took place between your

unknown acid and NaOH(aq) during the titration. DISCUSSION:

DISCUSSION: When the unknown was placed in the Erlenmeyer flask. We added 25ml water and 2drops phenolphthalein . so after we filled the burette with 1M NaOH then let it drip slowly by slowly in flask so it can be tinted pink. This shows that some compounds are too much for others and the mix with each other can make a clear solution change into pink by adding acid. At some point, the reaction solutions turn blue in the presence of starch. This helps to understand the fundamentals of chemical kinetics - the speeds at which reactions take place. I determined that reactant concentration is a major factor along with temperature (which is proportional to the average kinetic energy). The collision of the molecules is also very significant. The collision must have enough energy to break and form the proper bonds as well as have the accurate orientation when colliding (activation energy).When there are a greater number of reactant molecules available to react, there is a greater chance of a successful collision due to probability arguments. In the case of this study, the more KIO3 that was present per unit volume, the greater opportunity there was for a successful collision to happen. There were more successful collisions as evidenced by more product being formed in a shorter period of time (color change faster) . The graph of reaction rate vs. concentration confirms this increase-increase relationship. To conclude According to the data, the purpose was reached. The rate of a reaction is seen to increase when temperature or concentration are increased considering experimental error....