Download determination of the value ksp for feoh and more Lab Reports Chemistry in PDF only on Docsity! Lab Procedure: You will be working with strongly acidic and basic solutions in this lab. Safety glasses must be worn at all times and gloves should always be used when handling solutions. Precipitating Fe(OH)3: 1. Using a 10 mL volumetric pipet, add 10 mL of acidic 0.05M Fe(NO3)3 solution to each of three test tubes. (small flasks also work well) 2. Fill a 50 mL burette with 0.05M NaOH. 3. Slowly add base to the iron solution until a red-brown precipitate appears and remains upon stirring. 4. After 10 minutes, check to see that solid remains in the flask. If it has all redissolved, add a bit more base. 5. After your solutions have reached equilibrium. Centrifuge your samples to settle all the ppt to the bottom of the tubes. 6. Measure and record the pH of each solution with a pH meter. 7. When directed by the lab instructor, take your solutions to the AA to be tested. Calibration Curve: • Normally, I would have you create your own calibration curve. • We only have one AA, therefore the following solutions will be prepared for you. • You must: i. Calculate the [Fe3+] ii. measure the Abs iii. Create the actual calibration curve plot. • Y-axis = Abs • X-axis = [Fe3+] iv. Determine the best fit function for the data. • Linear • 2nd order Polynomial • Make sure to attach both plots mL of 0.10 M Fe3+ mL of 0.05 M HNO3 [Fe3+] Abs 15 Dilute to 25 mL 10 Dilute to 25 mL 5 Dilute to 25 mL 2 Dilute to 25 mL 1 Dilute to 25 mL put flask On blankpp. # fel0H3() Fe+ 30H isa) k3p =[Fe3+]2017-3 ↑ 1 is ove PJH PH 0.84 1.849 8.82 1.825 0.87 1,084 8.885 8,989 Calculations: 1. Convert pH to [OH-] 14 = pH + pOH pOH = - log [OH-] [OH-] = 10-pOH 2. Convert Abs of your sample to [Fe3+] using your calibration curve. • Using the best fit function, plug in your abs as your Y value and calculate the X value. • The X value will be equal to the [Fe3+] 3. Determining the average Ksp Ksp = [Fe3+][OH-]3 “Plug-&-Chug” 4. Calculate the average Ksp 5. Calculate your % error based upon the literature value for the Ksp(Fe(OH)3) y =mx +b =y = 1.35392 +0.9857 &y =Ax+Dx +C:y= -34.839x2+3.2611x +0.974 fel0H3() Fe+ 30H isa) k3p =[Fe3+]2017-3 ↑ post & ABS- Calcurve pH Run RUD 2 Run3 14 =3.27 + pOH 14 =3.38 + POA 14=3.37 +p0H pOH =10.73 POH =10.62 pOH=10.43 [8H-] =15 - 10.73 2017-1 =1.84 x 16 281] =18-18.52 2015:16 - 10.63 2014-3 =2.48x18 " SOHI =2.34x18- 8.911 = -34.839x2+ 3.26148.974 0.922:-34.839x243.2671 +0.9740.916 = -34.839x243.2671x +0.974 =- 34.839x2+3.267148.863 = - 34.839x2 +3.2671x +0.852 - - 34.839+3.2671x +0.858 -11.35x0.063:3.26715x4x.3x0.854:3.2671x4x.x8.S 2(-34.839) 2(-34.839) =0.118 => 0.188 X =0.189 1sp:[fe](OH] 3 1sp:[fe"] (OH] 1sp:[fe"] (OH] 3 10. 118) (1.8xxis3 10.188) (2.48x18 -73 10.189) (2.34x 10-3 7.00x18-34 = 1.49x18- 33 = 1.48 x 18 - 33
