Titration method for chemistry lab report

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I have a lab report that is related to the last one I did. It that we used two methods to find the Ka of a known Acid in lab #8. now, I have chosen the titration method for lab #9 which I am asking now

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1 SNOOR ecat.montana.edu PPIMG_2017 59g Ni2+ 1 mol Ni2+ 0.201g Ni* 1 mol Ni** 1 mol Ni(DMG), = 0.0034 mol Ni(DMG), (2b) 7. Include a caption for all tables and figures. Correct: + + 2 Hydrogen Buffalo 1 Oxygen Buffalo 1 Water Buffalo Blazek 1 Figure 1: Funny cartoon found relevant to nothing. At end of document, in separate REFERENCES section: 1. Blazek, D. Loose Parts Comic, http://www.gocomics.com/looseparts/2012/07/30, retrieved 10 Jan. 2015. I do not care what citation format you use as long as I can search for whatever you are citing and find it (online, library, etc.) Correct: MacBook Pro 20 OOO DOO F4 F3 F5 F6 F7 F8 F10 F12 Ô $ % & * ( for :/: 2 4 5 6 7 8 9 0 W E R Y U 0 3.5/ LABORATORY 9 a Determination of K for an Unknown Weak Acid Objectives The objective of this laboratory is to: Use either a dilution or titration technique to determine the K for an unknown solid weak acid. Equipment and Materials ~2 grams of unknown 0.100 M NaOH 50 mL buret (for titration technique) 10.00 mL pipette 100 mL volumetric flask Phenolphthalein indicator 50 mL beaker 100 ml beaker • pH probe Introduction In the previous lab, you explored two separate techniques for determining the acid dissociation constant for a weak acid (K). In this lab, you will be given a small amount of solid weak acid and will need to choose one of the techniques to analyze the acid. D Part I. Making the Solution of Acid for Analysis 1. Weigh out approximately one gram of your solid unknown and put into your 100 mL volumetric flask. Record your mass in your lab notebook. Also be sure to record the molar mass given for your acid. 2. Add about 25 mL of deionized water to your flask, and dissolve your acid. Once the acid is dissolved, fill your volumetric flask to the 100 mL mark with deionized water. 3. Calculate the molarity of your solution based on the amount of solid used and record in your lab notebook. Foto 29.53 M hill Foil M=66526 too 752X 나 20412 1575333 ecat.montana.edu C arvan LAB REPORTS Your lab report must be grammatically correct and formatted according to this syllabus. Not following simple directions will result in a deduction of points. Unless otherwise stated, all lab reports must be typed! Reports must be written in third person and in past tense (ask me if you are unclear about this type of format). See the example I gave you. The grading rubric shown will be the one I grade off of every lab report (unless otherwise specified.) Introduction (2 pts) 2 CHMY143 1. What was done? (Briefly explain the title) 2. Why was it done? (Purpose) 3. How was it done? (Name the technique(s)/ methods used) 4. Why should I care? (Practical applications) Procedure and Observations (5 pts) 1. Length: 2-3 paragraphs of what was done and what was observed when you did it. 2. Sufficient details provided- experiment could be reproduced using write up. . 2 17 View as Text Download >> MacBook Pro 000 ODO 0 F3 DIN FB F10 F9 17 F12 F5 F6 F? component * & ( $ or do < 0 2 4 7 9 8 O To TE { W T R Y U Р 0 1 sis-Comparing the Met K and PK values for each of the runs you did using the th, Calculate and report an average pk for your dilutions. 39226513 AVE 4.3 638 2 1 04.10 G 143 Experimental Chemistry Part II. Analyzing Your Acid Solution Use the procedure you created for your chosen technique to analyze your acid. Be 1. sure to record all important data and results in your lab notebook. Be sure to report both the K and pK values in your write-up. 2. If you need to make any adjustments to your procedure, be sure to note them in your lab notebook so that you can report them in your lab write-up. ecat.montana.edu C 3) Label equations, figures/graphs, tables, and include appropriate caption 4) Bold & capitalize headers 5) Cite your references! 6) The top of your report should be written in the following way (centered): TITLE OF THE EXPERIMENT CHMY 141-0XX TA: I. Heart Chemistry **/**/18 7. Do NOT write your name on the front of a handout lab report. On the back of your report, you will handwrite (or type) your name and your lab partner's name. . 1. Reports should be written using complete sentences. You should always use past tense, third person, passive voice. You should never write the procedure in an “instructional” manner. Correct: Incorrect: Incorrect: The reaction mixture was treated with.. I treated the reaction mixture with... Treat the product with... 2. The introduction/procedure should tell what you did. Not what “will be done.' Correct: Incorrect: The boiling point was determined with the thermistor. The boiling point will be determined using the thermistor. 3. Do not use contractions (won't, don't, can't). 4. Label all equations. You do not need to put a caption on equations. 1 5 17 View as Text Download MacBook Pro 80 F3 000 DOO DII F8 A F1 F5 F6 FZ F9 F10 F1 @ $ % & #3 < 0 2 4 5 7 8 9 0 W E R T Y U 0 Р
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Hi,I am sending you the Final report. You will find two reports. The only difference is in the units. I the first one units were written as 22 g/mol NaOH, while in the second one the units were written g/mol 22 NaOH (I realized that your supervisor expects to write like that).Text me if you need some edits .)

CHMY 141-0XX
TA: I. Heart Chemistry
In this experiment, the determination of Ka for an unknown weak acid was carried out. The
determination was based on titration techniques by using a strong base, NaOH. The pKa is characteristic
of the particular acid and can be used for determination of unknown acid. Also, the determination of Ka
is important for expressing the strength of the acid. So the main purpose of the experiment was to
determine the Ka of an unknown acid. The strength of the acid is directly connected to its solubility in
water which is important for possible application in pharmacy, industry, etc.


The determination was based on titration techniques to determine the Ka for a solid week acid. Into the
volumetric flask, it was measured 1.075 g of the evaluated solid week acid. The molar mass of the
substance is 204.2 g/mol. In the next step the solid was dissolved with 25 mL of deionized water into the
volumetric flask (100 mL) and finally filled up to the mark with deionized water.
In the cleaned and dried a 100 mL beaker it was pipette 20 mL of HA by using two 10 mL portions. Two
drops of the indicator (phenolphthalein) were added. Then, the previously cleaned and dried buret was
filled with the 0.100 M NaOH solution. The purging of the potential presented bubbles in the tip was
done by run same base into the waste beaker. The Starting Volume of buret was recorded. After the
adding of 4 mL of NaOH solution, the exact volume was recorded to the nearest 0.02 mL which
represented the Final Volume for the data table. The pH was measured using the pH indicator. The
experiment was repeated 5 more times by subsequent addition of a base in 2 ml increments. For each
experiment, the Starting Volume, Final Volume and the pH were recorded and are given in Table 1.

The data were obtained during the process of titration of unknown solid acid. The titration was based on
the application of a strong base. The measurements of pH were done using the pH probe. In Table 1 it is
presented the results obtained in this study. The average value of pH was 4.72. It the table it was given
the amounts of NaOH added before each pH measurement.

Table 1. The results obtained during the pKa determination for an unknown weak acid


Volume (mL)

Final Volume











The Ka was calculated taking into consideration the pH value. The reaction between weak acid (HAc) and
the strong base (OH-) (acid-base) neutralization was used for pKa calculation by using the HendersonHasselbalch equation (equation 1). Furthermore, by using equation 2 it was calculated the Ka of the
unknown solid acid.
[𝐴− ]

𝑝𝐻 = 𝑝𝐾𝑎 + 𝑙𝑜𝑔 [𝐻𝐴]


𝑝𝐾𝑎 = − log 𝐾𝑎


The following calculations were used for [A-] and [HA] concentrations calculation after each addition of
NaOH. Those values were used for pKa calculations. The calculation was given only for the first trial as
the same calculations were done for the other trials. The molarity of the acid solution before adding the
reactant (NaOH) was calculated to be 0.05 mol/dm3 by using equation 3.

m (HA) = 1.075 g
M (HA) = 204.2 g/mol
n (HA) = m (HA) / M (HA) = 0.005 mol
V (HA + deionized water) = 100 mL = 0.1 L
[HA] = n (HA) / V (HA + deionized water) = 0.05 mol/dm3
The morality of [A-] was calculated by using equation 4.
1st NaOH addition


Molarity (NaOH) = 0.01 mol/L
V (NaOH) = 4.02 ml= 4.02x10-3 L
n (NaOH) = 0.01 mol/L x 4.02x10-3 L =4.02x10-5 mol
n (NaOH) = n (A-) = 4.02x10-5 mol
V total = 20 ml + 4.02 mL = 24.02 mL = 24.02 X 10-3 L
[A-] = 4.02x10-5 mol /24.02 X 10-3 L = 1.67 x10-3 mol/dm3


The molarity of the acid solution after adding the reactant (NaOH) was calculated by using equation 5.

n (HA) = molarity (HA) x V (sample) = 0.05 mol/dm3 x 20x10-3 L=1.05 x10-3 mol
[HA] = (n (HA) – n (NaOH)) / Vtotal
= (1.05 x10-3 mol-4.02x10-5 mol)/ 24.02 X 10-3 L =3.26 x 10-2 mol/dm3


pKa =pH- (log [A-]/[HA]) = 4.246 – (log ([1.67 x10-3 mol/dm3]/[ 3.26 x 10-2 mol/dm3]))= 5.65
Ka = 10 (-pKa)= 2.25x10-6
It is important mentioning that the phenolphthalein indicator has changed the color to purple when
exposed to acid solutions (reached the equivalence point).
The obtained pKa value was compared with the literature published data [1]. According to the published
data, citric acid has a pKa value of 5.40. Based on the reported values the percentage error was
calculated (equation 6):
%𝑒𝑟𝑟𝑜𝑟 =

𝑝𝐾𝑎𝑡ℎ𝑖𝑠 𝑠𝑡𝑢𝑑𝑦 − 𝑝𝐾𝑎𝑙𝑖𝑡𝑒𝑟𝑎𝑡𝑢𝑟𝑒
5.68 − 5.40
× 100% =
× 100% = 5.2%

The possible error could be related to the measurement uncertainty of pH as this value play an
important role in pKa evaluation

The proposed t...

Just what I was looking for! Super helpful.


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