Part I: Using KHP for StandardizationShow all calculations on back of page and attach additional pagesas necessary.
Trial 1
Trial 2
Trial 3
Mass of KHP (g)
# Moles of NaOH used each trial
0.0215
Average Molarity:0.3564Average Deviation: 0.0143Percent Average Deviation (RAD): 1.43%Part II: Concentration of HCl Using Standard NaOHShow all calculations on back of page and attach additional pagesas necessary.Molarity of Standard NaOH solution: 0.3564
Trial 1
Trial 2
Trial 3
Volume of NaOH solution in each flask (L)
- Please Help With The Abstract Introduction And Experiment Summary Of Chem 131 Experiment 9 Acid Base Titration Stan 1 (148.38 KiB) Viewed 31 times
Exp. No. Name detox Titoret 107 basi determine the molarity of a solution of unknown te rentration by performing acid-base titration. Lab Partner Procedure this procedure can be found on page 173-124 of dala below. Deck Part II Standardization of Na Alt Using KHP #2 #1 0.3468 g Volume of NaOH used (ML) Ratio of Mass KHP /volume of Naolt used Cg KH+Phil 6-02686 Locker/ Desk No. Mass of KHP(g) Initial buret reading (m2) 13-21 mL 27-15ml 41.42 fincel 12.91ml 14.54 mul 13.67 10-02454 Part I: Uusing KHP se Standardization. 10.02459 Mass of # Moles of KCHP (moles). Moles of Naolt use each trial 6-006879 6-0050316-004720 volume of NaD It Solution used quid 0-01291 6-01454 6-01367 Molarity Nab it in each trial 0-31 19 10-3466 6-3453 0-6111 Average molarity beviation from average mclarity 6.0213 Average Dwviation percentage average divication 45 Course B Section No. # 1 #2 0.34689 6-3376 0.6048796-005031 0.004720 #3 03355 Trial 26-35769 14-54 m2 trial 30.33839 13-67 ml #3 0.3576 g 0.33559 13.21 0-3564 0-0104 0-6143 1.43% Mass ratio trial 1 → 0-3468 g = 0·026862897 0-02586 %/mL 12-94mL 0.07459%L 0.0243427944≈ 0.02454% = 6.624594 2228002169
10 determine the matcurity of a solution of unknown concentration by performing acid-base titration. Procedures the proceduse can be found on page 113-124 of data belossart II -> Concentration of HCI using Standard N₂OH Molarity of NaOlt from Part I = 6-3569 Trial It 1 Initial buret reading of HCL (MD 6.46 Single of HCL used (one) karet reading of HCL (ML) 25.50 Initial buret reading of Noelt (ml) volume of Neading of NaOH (ml) used 43.20 ratio of Volume HCL/vola Na OH 0.5810 Ratio of volume HCl/N₂o Hi Trial Trial = Signature Molarity of Standard NaOH Solution: 6+3564 0.3564 1 2 3 0-01600 0-01660 6-1636 6.6454 Volure of Naolt Solution in egch (20-04320 0·04310 0-04490 # moles of NaOlt in each flask 0-01540 0·01607 # moles of HCL to reach endpoint 6.0154 06.01607 Volume of HCL Solution to rechang Per-02510 0-02490 0-02300 6-6400 Molori by HCL in each trial Average molarity Deviation from Average. Average Deviation Percentage Average Deviation molosity 0-319% Trial 3 23.00 44-26 0.20 43.40 Date 24-96 =0-5521064302 = 0.5521 45.10 2 0-30 25.20 24-90 0.50 45-40 45.10 6-5521 = 23-10 = 0.5810185 185 = 0-5810 43.20 May THE HAYDEN-MCNEIL STUDENT LAB NOTEBOOK 0-162* 0-213 21-3% Witness/TA 99/3/2021" 3 6.30 25-30 23.00 0:30 45-20 44.90 10-5568 0.5561928 1310-5568 Date Note: Place fold-over back cover under copy sheet before writing Standart
ACID-BASE TITRATION: STANDARDIZATION Experiment 9 AND USE OF A SOLUTION Purpose: performing acid-base titrations. To determine the molarity of a solution of unknown concentration by Performance Goals Gain titration skills Use acid-base titration to standardize a NaOH solution Use a standard solution to determine the concentration of another solution Calculate molar concentration using titration data . Introduction Titration is an analytical technique for determining the concentration of a solution (analyte) by measuring the volume required to completely react with a standard, which could be a solid of high purity or a solution of known concentration. The concentration of the analyte is calculated based on the stoichiometry of the reaction between the analyte and the standard. Different types of titrations such as acid-base titrations and oxidation-reduction titrations have been utilized in chemical analyses. The emphasis here is on acid-base titration. Acid-base titration is called neutralization when the reaction is between a strong acid and a strong base cause a neutral salt and water are the only products. During the reaction, there is a point when the number of moles of acid (II ions) equals the number of moles of base (OH ions) this is known as the equivalence point of the reaction. For example, in the reaction between HCI and NaOH shown in Equation 9.1, the number of moles of H" will be the same as the number of moles OH at the equivalence point since the mole ratio between the two is 1:1. For a reaction between a diprotic acid such as sulfuric acid (H₂SO4) that contains two moles of H+ ions per mole of H₂SO4 and a base such as NaOH that contains one mole of OH ions per mole of NaOH, the mole ratio will be 1:2 as shown by the respective coefficients in Equation 9.2. HCl(aq) + NaOH(aq) H₂SO4(aq) + 2NaOH(aq) + H₂O(7) → NaCl(aq) → Na2SO4(aq) + 2H₂O(1) (9.1) (9.2) A chemical substance called an indicator is used to determine the equivalence point. An indicator is a solution that changes color based on the nature (acidity or basicity) of the solution. For acid-base titrations the indicators used are weak acids or weak bases. They have one color in acidic solutions and another color in basic solutions. For instance, an acid-base indicator represented by HIn in its acid form undergoes a change when put in water as illustrated by Equation 9.3. + H₂O(1) H3O*(aq) (9.3) HIn(aq) acid form In (aq) + base form The indicator, phenolphthalein, is often utilized when strong or weak acids and strong bases are used in a titration. Phenolphthalein is colorless in its acid form but is pink in its base form which exists in the presence of excess base. When phenolphthalein changes from colorless to
Experiment 9: ACID-BASE TITRATION: STANDARDIZATION a pale pink color as a base is added to an acid solution, it is an indication that the mixture has just passed the equivalence point. This observable instant is referred to as the endpoint. An indicator is chosen such that the observable endpoint occurs at or very close to the stoichiometric equivalence point of the reaction. When phenolphthalein is used as an indicator, if the titration is carried to a bright pink, it is an indication that too much base has been added. Solutions of strong bases, such as NaOH, are usually made by dissolving the solid in water. Presumably its concentration can be calculated from the mass of the solid and the volume of the solution produced. However, the solid NaOH is hygroscopic (easily absorb moisture from air.) In addition, the carbon dioxide that is naturally dissolved in water further changes the acidity of the solution. Thus, the actual concentration of the NaOH solution has to be determined experimentally using a process called standardization. To standardize a base solution such as NaOH, an acid whose amount can be determined to a high degree of accuracy (called a primary standard) is needed. Potassium hydrogen phthalate (KHP), a monoprotic acid, is often used as a primary standard for titrating bases. The reaction between sodium hydroxide and KHP solutions proceeds according to the following reaction (Equation 9.4). brebowa sch bro avadano C OH LOK bao bi C 11 O NaOH O ONa OK H₂O (9.4) KHP (MM 204.2 g/mol) Alternatively, solutions of HCI with known concentration can be purchased commercially and used to standardize basic solutions. Such solutions are referred to as standard solutions. In this experiment an acid-base titration will be conducted in order to determine the precise molar concentration of a sodium hydroxide solution (that is, to standardize NaOH). The standardization will be carried out using KHP as the primary standard and using a standard HCl solution of known concentration. NEIGH Equipment/Materials Using KHP as standard: 50-mL buret, 250-mL Erlenmeyer flasks (3), ring stand, buret clamp, potassium hydrogen phthalate (KHP), NaOH solution (unknown concentration), phenolphthalein, wash bottle with deionized water, bar magnet and magnetic stir plate Using standard NaOH: Two 50-mL burets, 250-mL Erlenmeyer flasks (3), 250-mL beakers (2), ring stand, buret clamp, phenolphthalein, HCl solution (unknown concentration), standard NaOH solution (from Part I), bar magnet and magnetic stir plate
Experiment 9: ACID-BASE TITRATION: STANDARDIZATION Procedure This experiment will be done over two weeks. Part I will be done the first and Part II will be done the second week. Cleaning the Buret: Your instructor or lab technician will indicate whether the burets supplied to you are clean. If they are not, follow the instructions below on how to clean them. In order to clean a buret the stopcock of the buret should be turned perpendicular to the buret (i.e. to close it). Deionized or distilled water should be run down the sides of the buret using a wash bottle. Water should be poured out of the buret, rotating it so that water runs along the entire inner surface. Caution must be exercised not to hit the buret on the sink or any other objects. The above process should be repeated two more times. The buret should be filled with water. If a meniscus forms and water does not form beads on the sides, the buret is clean. If the buret is not clean, then the buret should be cleaned with soap and water followed by rinsing with deionized water three times. Make sure that no residue of soap remains inside the buret. The stopcock and the tip need to be cleaned by opening the stopcock and letting water flow through the stopcock and tip into a beaker. Setting up the buret: Setting up the buret correctly is important for a successful acid- base titration. Figure 9.1 illustrates correct set up of a buret. The lower tip of the buret should just be in the mouth of the Erlenmeyer flask containing the analyte. magnetic stir plate T Figure 9.1 If a standard NaOH solution is used, there would be a second buret fastened to the other side of the buret clamp as shown in Figure 9.2.
Experiment 9: ACID-BASE TITRATION: STANDARDIZATION Part I: Standardization of NaOH Using KHP 1. Under the "Data" section in your lab notebook, create a data table with the following headings: buret 0.61 Trial Mass of KHP (g) Initial buret reading (ml) Final buret reading (ml) Volume of NaOH used (mL) Ratio of Mass KHP/Volume of NaOH used (g KHP/mL NaOH) 2. Label a 250-mL beaker as "NaOH" and a 400-ml beaker as "Waste." 3. Clean the buret according to the instructions provided above. Then rinse the buret with two 10-mL portions of the NaOH solution. Drain the NaOH into the waste beaker. #1 #2 #3 0-3465 035 74 023 0-30 13-21 27-75 13-2127-715441-4224 114-54-113-673 10:02.684 0:621590-021134 12-20 4. Set up a ring stand with a buret clamp and place the clean buret in the buret clamp. Position a magnetic stir plate in such a manner that the buret tip is directly over the center of the stir plate as shown in Figure 9.1. 5. Fill the buret with the NaOH solution. Be sure to lower the buret so that you that you are not pouring the liquid above your head. Run some of the liquid through the tip to fill the void. If you use a funnel, always remove it before you make the initial reading. B Record the initial buret reading. This should be close to the zero line to insure that you have enough liquid to complete a titration run. Reminder: the buret is calibrated in increments of 0.1 mL and therefore can be read to 2 decimal places. 7. Label three clean 250-mL. Erlenmeyer flasks (labeled as 1, 2, and 3). They do not need to be dry. 8. Tare a plastic weighing boat to zero. Add about 0.3-0.4 g of KHP and record the precise mass under Trial 1 in the data table. Transfer the KHP sample carefully into Erlenmeyer Flask 1. 9. Repeat Step 8 for Flasks # 2 and 3. Be sure to put the second mass in Flask 2 and the third mass in Flask 3. 116 10, Add about 50 mL of deionized water to each flask (use graduations on the flask) and 3 drops of phenolphthalein indicator to each flask. Slide a clean magnetic stir bar into the Flask 1 taking care not to let any solution splash out. It may be necessary to warm the flasks slightly on a hot plate in order to dissolve the KHP. However, the solutions must cool back to room temperature before you begin the titration.
Experiment 9: ACID-BASE TITRATION: STANDARDIZATION 11. Check the initial buret reading. If it has changed, your buret has a leak. You should not use a leaky buret. Report this to your instructor who might direct you to change it 12. Place Flask 1 on the magnetic stir plate. Turn on the magnetic stirrer and adjust it so that the magnet stirs smoothly at a moderate speed. 13. Titrate the sample in Flask I with NaOH solution from the buret until the first shade of pink persists for 30 seconds. As you near the endpoint, use the wash bottle with deionized water to wash down any splatter that may have collected on the inside surface of the flask. Record the final buret reading. Remove the bar magnet from the flask and rinse it well with deionized water. 14. Repeat Steps 12 and 13 with Flasks 2 and 3. Be sure to add the cleaned bar magnet to each flask. 15. Calculate the ratio of the mass of KHP (g) to volume of NaOH (mL) for each trial. The volumes of NaOH used in the three trials might be different because slightly different masses of fKHP might be used. The ratio, however, should be the same. This calculation will indicate whether or not all three trials are acceptable and whether more trials are necessary. The ratios should not differ by more than 0.001 g KHP/mL NaOH. This calculation must be performed before proceeding to do more trials. Clean-up 1. Pour waste into appropriately labeled containers. 2. Clean your glassware and rinse and return the burets to their proper location. 3. Ret all chemicals and equipment to their proper location. 4. Wash your hands before leaving the lab. Calculations for Using KHP for Standardization 1. Calculate the # mol of KHP by using the mass of KHP used in each trial and the molar mass. #mol KHP = # g of KHP 1 mol KHP molar mass of KHP 2. Find the # mol NaOH by using the relationship, #mol NaOH = #mol KHP 3. Find the volume of NaOH used in each trial by subtracting the initial buret reading from the final buret reading; VNaOH = Final buret reading-Initial buret reading 4. Convert VNaOH in mL to L 5. Calculate molarity of NaOH by using the equation #mol NaOH Molarity of NaOH = To en Alternatively, molarity Molarity of NaOH= #g KHP #LNaOH soln of NaOH can be calculated by using the following setup: 1 mol KHP 10 mL NaOH molar mass KHP, g, 1L NaOH at 6. Calculate average molarity of NaOH. 1 mol NaOH 1 mol KHP 1 #ml NaOH
PARDASIC Experiment 9: ACID-BASE TITRATION: STANDARDIZATION Part II: Concentration of HCI Using Standard NaOH 1. Under the "Data" section in your lab notebook, create a data table similar to the following: 6. Molarity of NaOH from Part I => Trial # Initial buret reading of HCI (ml) Final buret reading of HCI (ml) Volume of HCI used (mL) Initial buret reading of NaOH (mL) Final buret reading of NaOH (mL) Volume of NaOH used (mL) Ratio of Volume HCI/Vol NaOH 2. Obtain two 50.00-mL burets and set them up on a ring stand fitted with a buret clamp as shown in Figure 9.2. Place gummed labels provided on the buret clamp to label one buret as HCl and one as NaOH. Next, label a 250- mL beaker as HCI and a 250-ml beaker as NaOH. Both beakers must be clean and dry. Finally, label a 400-ml beaker as "Waste." It is essential that you keep all your equipment clearly marked. 3. Position a magnetic stir plate under the NaOH buret. Do not put the Erlenmeyer flask there as yet. √4. Record the concentration of the NaOH in your data table. #1 0.40 ATTRO 43.40 0.5810 NaOH #2 0-30 25.20 0 45-40 45-10 #3 6.30 25:30 25-60 Figure 9.2 2 449011 0-53216-556811 HCI ✓5. Pour about 100 mL of the standard NaOH solution into the NaOH beaker, and 100 mL of the HCl solution into the HCl beaker. Do not get your containers mixed up. Use two 10-mL portions of the acid to rinse the HCI buret and two 10-mL portions of the base to rinse the NaOH buret and then fill the HCI buret with HCl and the NaOH buret with NaOH. For each buret, run a little of the solution through the tip to fill the void. Record the initial reading of each buret under Trial 1 in your data table. Make sure the reading is close to zero. Note: Because the burets are calibrated in increments of 0.1 mL, each buret reading should have 2 decimal places.
MIT Experiment 9: ACID-BASE TITRATION: STANDARDIZATION 7. Obtain a 250-mL. Erlenmeyer flask from your drawer. Clean it thoroughly with detergent using a test tube brush, and rinse thoroughly with tap water. Finally, rinse it several times with small portions of deionized water. This flask does not need to be dried. Obtain a wash bottle of deionized water and have it next to you, ready for use. 8. Allow the HCI solution to drain into the Erlenmeyer flask until the meniscus is around 25 mL. If there are any drops hanging on the tip of the buret, touch it to the inside wall of the Erlenmeyer. You do not need to record the buret reading as yet. 9. Carefully slide a magnetic stir bar into the Erlenmeyer flask, taking care not to allow any solution to splash out. 10. Add one or two drops of phenolphthalein indicator to the flask and place the flask on the magnetic stir plate with the tip of the buret just inside the mouth of the flask. Turn the magnetic stirrer on gradually to medium speed. 11. Slowly add the NaOH solution from the buret to the flask drop by drop. Initially you will see a pink color appear and disappear as the NaOH gets neutralized by the HCI in the flask. As you near the endpoint, use the wash bottle of deionized water to wash down any splatter that may have collected on the inside surface of the flask. 12. When the pink color is staying longer, slow down the addition of the drops so that at the end point you have time to turn off the stopcock before the next drop is added. Continue adding the NaOH solution until the color changes to a pale pink that persists after 30 seconds of stirring. This should be a very pale pink; the paler, the better. 13. If it is darker than what your instructor has shown you, it means you have added too much base and have past the endpoint. Normally this means you have to throw out the solution and start over; however, since you have the acid in the other buret, all you have to do is add one or two drops of acid to the flask to remove the pink color, and you can try again to add just enough base to reach the pale pink. 14. After you have reached a satisfactory end point, record the final buret reading on each buret to the nearest 0.01 mL. 15. Calculate the volume dispensed from each buret (by subtracting the initial buret reading from final buret reading). 16. Repeat Steps 6 to 15 for Trials 2 and 3 using a clean 250-mL Erlenmeyer flask for each trial. The bar magnet should be carefully rinsed with deionized water before inserting into the flasks.
Experiment 9: ACID-BASE TITRATION: STANDARDIZATION 17. Then, calculate the ratio of the volume of HCl to volume of NaOH. These ratios should not differ by more than 0.04. If they do, additional titrations may be necessary before you go on. YOU MUST DO THESE CALCULATIONS BEFORE YOU DO MORE TRIALS. Clean-up 1. Discard the contents of the Erlenmeyer flask in the sink as it is near neutral. Take care that the stir bar does not go down the drain. Use a magnetic wand to remove the bar magnet. 2. Clean your glassware and rinse the buret before returning them. Return all chemicals and equipment to their proper location. 4. Wash your hands before leaving the lab. 3. Calculations for HCI Concentration 1. Calculate the number of moles of NaOH by using the volume of standard NaOH used in each trial and its molarity #mol NaOH = molarity of NaOH x volume NaOH (L) 2. Find the number of moles HCI from the number of moles of NaOH (See Equation 9.1). 3. Calculate molarity of HCl of each trial by using the equation: # mol HCl Molarity volume HCl solution (L) 4. Calculate the average molarity of HCl. 5. Calculate the deviation from the mean for of each trial, the average deviation and the relative average deviation (RAD or RMD). Refer to Experiment #1 for these calculations.
Name CHEM 131 Sec; Data and Results Part I: Using KHP for Standardization Show all calculations on back of page and attach additional pages as necessary. 6/30/2022 Mass of KHP (g) # Moles of KHP (moles) # Moles of NaOH used each trial Volume of NaOH solution used each trial (L) Molarity NaOH in each trial Average Molarity Deviation from Average Molarity Average Deviation Percent Average Deviation (RAD) Volume of NaOH solution in each flask (L) #Moles of NaOH in each flask #Moles of HCl to reach endpoint Volume of HCl solution to reach endpoint (L) Molarity HCl in each trial Average Molarity Deviation from Average Molarity Average Deviation Percent Average Deviation (RAD) Date #3 0.3468 6-3576 16-3333 2 0.00419770.00 503) 6-0047203 0.004879|0-0030310-0047294 6-612916-6145446.61367 6-37776-3460 6-34534 0-3564 0·0215/6.0104/6-0111/8 0.0143 1-43% Part II: Concentration of HCI Using Standard NaOH 1/os/Show all calculations on back of page and attach additional pages as necessary. Molarity of Standard NaOH solution: 0.3564 #1 • In your note book #12 #3 19 #2 0.04-3200-045106.04490 10.015806-01667/0.016005 0.01540 6.016010-016004 0.025/0 0.024900-02500 16-16361 0.64540.64006 0.483 10-31910-1620-157 01213 16 21-3% L R U