(Solved): im trying to figure out if i set up question 5 correctly and how to start the rest of the questuons. ...

LAB 19: TITRATION Goals We often mix a solution of unknown 1. Better understand molarity concentration with a solution of known concentration to determine the concentration of the unknown solution. If 2. Perform a simple titration the solutions are an acid and a base, the 3. Calculate the molarity of the vinegar solutions are mixed until the solution is neutral neither acidic nor basic. For an acid that donates one $$H$$ ion per molecule (is 4. Calculate the percent of acetic acid in monoprotic) and a base that receives one the vinegar HI lon per molecule, the neutral solution (the end point) is when the moles of acid Materials and Equipment equal the moles of base. The solution will have the same amount of acid as base. Reagents: $$0.1\mathrm{M}$$ sodium hydroxide, $$\mathrm{NaOH}$$ (Equation 19.3) moles aw $${}^{?m}$$ moles suw Phenolphthalein indicator paper Equations $$19.2$$ and $$19.3$$ can be Beaker, 15-mL combined to give: Beaker, 30-mL Graduated cylinder, 10-mL Graduated pipet (Equation 19.4) $$M_{\text{mad }}{V}_{\text{au }}=M_{\text{san }}{V}_{\text{Aur }}$$ Plastic toothpicks Reaction plate, 24 well Consider a neutral solution of an Materials Not Included acid and a base. If we know the volume of the acid added, the molarity of the base, and the volume of the base added, Distilled water we can easily calculate the molarity of White paper the acid. In this example, the acid is of White (clear) vinegar unknown concentration, and the base of known concentration. Introduction In this experiment you will use molarity to help find the acid concentration of a sample of vinegar. We define molarity Procedure. as the moles of solute per liter of solution: 1. The dropping bottles must be calibrated. With the graduated cylinder and the dropping bottle containing distilled (Equation 19.1) $$M=$$ moles water, count the number of drops of water it takes for $$1\mathrm{mL}$$. Hold the bottle where Mis the molarity, vertically so the drop size is consistent. of solute, and See Figure 19,1. Do this twice and of solute, and Vis the volume of solution in take the average. Record this data in liters. This can be rearranged to give: the Questions section. If the number (Equation 19.2) Moles $$=M$$ of drops differs by more than one, the 2. Pour several $$\mathrm{mL}$$ of vinegar into a small beaker. Draw $$1\mathrm{mL}$$ of vinegar up into the graduated pipet (see Figure 19.2) and put it into the second beaker. Carefully measure $$9\mathrm{mL}$$ of distilled water in the graduated cylinder and put it into the second beaker with the.1 $$\mathrm{mL}$$ of vinegar. Mix this with the graduated pipet. The concentration of the solution in this beaker is now one-tenth that of the original vinegar. 3. Use the graduated pipet to put $$1\mathrm{mL}$$ of the diluted vinegar into wells D1 and D2. See Figure 19.3. Put the reaction plate on a piece of white paper; this will make it easier to observe the color change. 4. Cut or tear two pieces approximately 5 $$\mathrm{mm}$$ long off a strip of phenolphthalein indicator paper and drop them into the solutions in wells D1 and D2. These are the wells with the diluted vinegar. 5. Titration will be done with the dropping bottle containing 0.1 $$\mathrm{MNaOH}$$. Hold the dropping bottle vertically over well D1 and count the drops until the first pink color shows. See Figure 19.4. Then slowly stir with a toothpick and add drops of $$0.1\mathrm{MNaOH}$$ (continue to count the drops) until the faint pink color stays for more than 30 seconds. If you go past the faint pink color, you will need to repeat the titration. Record the total number of drops of the titrant. (The $$\mathrm{NaOH}$$ solution is the titrant, since it is used to titrate the diluted vinegar.) 6. Repeat Procedure 5 for well D2. Record the drops. 7. Average and record the results from Procedures 5 and 6 . 1. Drops in $$1\mathrm{mL}$$ from a dropping bottle, Procedure 1: Trial $$12.5$$ drops $$/\mathrm{mL}$$ Trial $$224drops/mL$$ Average $$24.5\mathrm{drops}/\mathrm{mL}24.5$$ 2. From Question 1, the volume of one drop in $$\mathrm{mL}$$ is: $$\mathrm{mL}/\mathrm{drop}$$ 3. Drops of titrant from Procedures 5, 6, and 7 : 4. Use Questions 2 and 3 to calculate the average volume (in $$\mathrm{mL}$$ ) of titrant that was used. Volume of titrant $$\mathrm{0.9.2.5}\mathrm{mL}$$ $$0.93\mathrm{mL}$$ 5. You now know the volume of the diluted vinegar, the molarity of the base, and the volume of the titrant (Procedure 4). Calculate the molarity of the acetic acid in the diluted vinegar. Molarity of acetic acid in the diluted vinegar $$0.076\mathrm{M}$$ 6. Use the answer from Question 5 to find the molarity of the undiluted vinegar. Molarity of undiluted vinegar M 7. The formula for acetic acid is $${\mathrm{CH}}_3\mathrm{COOH}$$. Calculate the molar mass. Molar mass $$g/\mathrm{mole}$$ 8. From the information in Questions 6 and 7, calculate the mass of the acetic acid in 1 liter of undiluted vinegar. Mass of acetic acid in 1 L of undiluted vinegar 9 9. Find the percent of acetic acid in the undiluted vinegar. Remember that the mass of one liter of water is $$1000\mathrm{g}$$. Percent of acetic acid in vinegar $$\%$$ 10. How does the percent given on the bottle compare with the percent you measured?