Characterization of a Weak AcidIntroductionThe main goals of this experiment are to understand the titration curve of a weak acid, calculate the molar mass of the weak acid, calculate the Ka value of an unknown weak acid, and use the molar mass and Ka values to identify the acid. The determination of the dissociation constant Ka is an important concept in this lab. Thedissociation constant is the extent that, for example, a weak acid dissociates in a solution into ions. Also the molar mass is the amount of grams in one mole of a solution. These will be determined by titrating a weak acid into a strong base, NaOH,first by using phenolphthalein, then a pH probe. The equivalence point is the point atwhich the concentration of the acid is equal to the concentration of the base. The amount of acid used will be massed, and then molar mass can be determined1. The general formula for the addition of a weak acid and a strong base is as follows for a monoprotic acid. A monoprotic acid is one that loses one proton.1 HA + OH-  H2O + A-(1)The Ka also can be expressed as follow. Also the H+ ions can be calculated by the observed pH at any moment with the following reaction1.Ka = [H+][A-]/[HA] (2)The concentration of HA can also be calculated at any time in the following equation.1 Original molesof acid−moles HA consumedvolume(3)In order to find the many things in a titration—when a measured amount of unknown substance is slowly added to another known solution until equivalence is reached—by finding the halfway point. The halfway point is the point at which the amount of solution added needed to reach equivalence point is half. At this point Ka=[H+] and pKa=pH. Also if the [H+] has been calculated the following can be used to determine pH1:pH = -ln[H+] (4)For a diprotic acid—an acid that loses two protons per molecule. This followsthe following equations for titration reaction for the first and second equivalence points respectively1:2H2A + OH-  A2- + H2O (5)HA- + OH-  A2- + H2O (6)There are two dissociation constants Ka1, and Ka2 for a diprotic acid and can be defined by the following1:Ka1 = [H+][HA-]/[H2A](7)Ka2 = [H+][HA2-]/[HA-] (8)For a diprotic acid there are two equivalence points because it dissociates twice. In this case the second halfway point is important for the reason that moles of HA- is equal to moles of A2- and because of this concentrations are equal. Therefore Ka2=[H+] and pKa2 = pH. pKa measures the strength of an acid. Also a detailed introduction can be found in the lab manual1. [H+] is the acid [A-] is the base.Titrations and neutralization reactions can be seen in many areas in the science world to determine many different things. In the Czech Republic, some scientists used a neutralization micro-titration to determine the nitrate content in different drinking wells. This was done to determine a scheme to remove these ions from this water2. Also because of the acidification of soils and surface water in Australia, indicator bas-field titrations are used to monitor the pH of water in the area, and ensure the pH does not go uncontrolled, and keep the water neutralized3. Finally in an experiment, experiment 223, a bacteria was emitting H+ sulfuric acid. Alkaline cations were then dumped into the lake and it was found to neutralize the lake, therefore neutralizing the bacteria4. 3Table of ReagentsReagent Molar Mass(g/mol)Density(g/mL)Melting point (ºC)Boiling Point (ºC)HazardsNaOH39.997 2.13 318 1388Very harmful if swallowedSevere irritation to skinPhenolphthalein 318.32 1.28 260 DecompIrritant to eyes and when ingestedKHP 204.22 1.636 295 Decomp Irritant to eyes, skin, and lingsH2O 18.02 1.00 0 100 Drowning in copious amounts of waterProcedure1. A detailed procedure can be found in the lab manual1. 2. The first way this will be performed is by manual titration.3. Prepare a solutiona. Make 1 L of 0.1 M NaOH from the stock solution provided and boiled DI water.b. Mix the solution vigorously to ensure the NaOH is not more dense in some areas than others. c. Place this in a Nalgene bottle and store in Nalgene bottle, as this solution will be standardized in the experiment.4. Weigh .0.3g of KHP and dissolve it in 70 mL of boiled DI water. Then prepare two more examples in this manner.5. Set up the titration apparatus as shown in the lab manual1. a. Items needed are a buret, a ring stand, buret clamp, a waste beaker(400 mL), 250 mL Erlenmeyer flsk, and a pH indicator. 6. Place a waste beaker under the buret and ensure the stopcock is closed.7. Add the .1 M NaOH solution into the buret and fill above the zero mark.8. Allow the buret to drain until the 5 mL mark is reached, then record the initial value.9. Add two to three drops of phenolphthalein to the each solution with KHP. Place one of these beakers below the buret10. Titrate slowly while mixing until the end point is reached with a pale pinkcolor. 411. If overshot, meaning the color is not pale pink it is darker pink, this titration must be redone. 12. Repeat with the other two beakers.13. Next, the titration will be performed using labquest. 14. Set up the titration shown in picture 5-4 in the lab manual. a. The necessary tools to perform this are a Vernier pH sensor, pH sensor stir paddle, stirring plate, ring stand, buret clamp, double valve buret (not the same as used for manual titrations) and vernier DropCounter. b. Plug the pH probe calculator and Dropcounter cables into labquest. 15. Calibrate the pH probea. Choose calibrate then pHb. Record the room temperaturec. Obtain the two buffers provided and use the label on the buffer to determine the correct pH. Calibrate using the two different pH’s d. Set the drip rate to a desired speed, and it should never be changedduring the experiment. e. Once set close the bottom valve empty graduated cylinder holding the NaOH, let 5-10 mL flow through the titration, 16. Weigh by difference .30g of unknown weak acid using analytical balance and record the exact mass, place in a 150 mL beaker17. Dissolve the weak acid in 70 mL of DI water from a volumetric pipet.18. Fill the buret with the NaOH solution19. Place beaker beneath dropCounter and attach pH probe to a stir paddle the n place the pH probe in the small hole. Begin stirring solution.20. Press graph on Lab Quest. And start reading pH21. Watch the curve as the pH probe collects data as the titration proceeds.22. Stop when it reaches 12 or 13.23. Insert a flash drive and export data24. Repeat two more