Titration of Unknown Weak Acid Start your procedure from this point if drected b

Question

Titration of Unknown Weak Acid Start your procedure from this point if drected by instructor. There willbeatotal of five titrations for this onelysis. Time vol Ttront (sec) domain Experiment 23 Ask you instructor if Method i is to be Vol Titront (nt) domainExperiment 24 or If you are going to use Experiment 24 then prepare the computer for data colection by lounching Logger Pro ond then inthe LoggerPro menu, open the experimental parometer under, Chemistry Verner/24a Acid-Base Titration embl with Tinuting the Unknown Weak Acid with Venner's ph probe three titrations alethetn ormation you calculated from pre-lob question m4, wegh out three samples of Your unknown ocid using Using the int his mass. This mass represents the amount that require opproximately 35-40 mL of your stondardzed NooH solution for titration Record the esses of weighing paper ond poper plus acid in your lob notebook (Show this to your instructor before proceeding) Tronsfer acids into clean, labeled de-mouth Erkenneyer flesk and then add enough desionized water to dssolve eech acid sample. Do not add indicator for this analysis. Note that the total somple 4iso20o g., then the ness needed to moke the solution for question W4. That is, if the answer to question Method 2 should amount to 0800gtotal. Nore: use the techniques used in the vermier activity lab to set up the verrier pH probe. Set up the Vernier interface th the pH probe. calibrate the meter ing PH4oond PH 10 buffers ond test-th buffer 70 Rinse the electrede with deierized ter ofter each triol Immerse the electrode in one f your unknown cid solutions. 23 is Ask structor, hich method in verrier you be using. Experiment 24a sPH s volme Titnert Eperrern Note sothat the spinringstirbor will not bump the frogle glass menbrane. See Figure 3. to position the electrode 23. amognetic stirrer and titrates the alrown cid th your stonderdzed NooH If you are using Experiment occurs hen the solution give pHneoding of 12 orefter have been diedPost the the flow is after the addition of titrant. This usually you con then use the equation: vol e (note addition bydividing the total volume titreted by the total time of the titration time to reach eq.pt) to find the corresponds to the equivalence poin point along the curve with the steepest sope. This point unins 24a, be sure record leb no ebook even though the data is stored in thecomputer. write detailed observators during the experiment. Save your file immediately in the computer and ther transfer the Excel before Refa the the onExeel unknown acid, following the same procedure before After coch titration be sure to sove your data transfer it to before continuing under the hood hove completed this portior of the experiment, pour the titration mixtures inno the waste antairer When you h Fourth and fifth titration of unknown weak deed toewurvaenrepevnt Nmatiens Take the unknown acid and wegh, to the tenth of mg, obout 19 mass. Place the ocidino 200 vokametre flask and then add sufficient deionized woter to dissolve the seld. Remember to use e volumetric flask for this procedure precision of the concentration. Shake and moke sure the solute dissolves and then mark The solution prepared wil be for triols4and 5 be not discard this stock selution urwil the experiment is completel pet 2500 ml of the solution into 125 ml Erlenmeyer flask or becker) Add 2-3 dreps of phenolphtholein indeator (recol from earlier work that Phenolphthalein is a in ond pink in basic solution thus the color chonge for the titration will be colorless to pink), Note that you do not need to continuously monitor the pHwith the pH probel Titrate of the pink color with your stondardized 01M NooHoogo. Record both the initial the solution to the at the equivalence point, De nat odd anymore and final buret velumes to the nearest 001 m. It is important that you stop titrant. Record the pH of this solution. he additional 2500 of the acidic solution from the 200 nL stock solution (made in the vokumetric fask) sokutin Erlenmeyer flosk on beaker containing the fourth titration. Next use the pH meter to determine the pHof the combined Recol that the pH needing for this solvtir satisfies the condition in equation 4Gbove Record this pH volue in your lob netebook 4) Repeat this procedure for the fifth trial using the same steps (2 through abave. Clean up location Turn off the computer, place ol vernier ewupment bor and return them to their original buret and transfer beaker into back in the box, and place on the instrvctor's table. Tronsfer ory NooH solution nemaining in your water. Drain the buret. the Discorded NooH Solvtion' beaker. Rinse your buret twice with top water and once with deienized Rinse the electrode With the stopcock open, clamp your buret to the support stond in an inverted position, so it can dran

Explanation / Answer

Post lab

1) If not all of acid is dissolved, less volume of base would be needed for neutralization and thus lower moles of acid would be calculated. This would thus give a higher molar mass of the unknown acid.

molar mass = weight of acid taken/moles of acid

2) An aliquot of stock solution of unknown acid was used for titration in this case which represents the acid solution. Another titration is performed by taking 25 ml again to the flask.

3) If less than 25 ml is taken, moles would be lower by titration and thus molar mass would be higher. Concentration of acid calculate would be higher and thus pKa would be higher.

4) Formation of carbonic acid would result in more base used for titration. So moles of acid would be higher, concentration of acid would be lower, and pKa would be higher.

5) If pH probes are not calibrated we would get error in molar mass measurement depending upon If the error reads value higher or lower than actual reading.

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.