*You should work in groups of no more than 3 students. Each individual is responsible for all data and information in their own booklet.

Transcription

1 Name Period 1

2 *You should work in groups of no more than 3 students. Each individual is responsible for all data and information in their own booklet. Pre-Lab Questions: What is the molarity equation? What element does an acid always start with? What ion does an acid produce in solution? What ion does a base produce in solution? What is an indicator? (In notes or p. 421 of chem book) Which indicator will we be using? What is the long measuring tube called we will put the base into? What is the name for the curvature of water in a glass container due to the attraction of molecules? What does [HCl] mean? What type of reaction is neutralization? What are the 2 products of neutralization? What is the chemical formula for sulfuric acid? When titrating, why should you repeat until your volumes are within 0.5 ml? Why should you use a volumetric flask to make your base instead of a beaker? 2

3 PART 1: Preparing a standard base solution. Show your calculations below and have your instructor check you off before you begin. Be very careful! Base: Prepare 250 ml of a 0.25 M solution. Use a volumetric flask that accurately measures 250 ml and pour the distilled water into a beaker. Calculate how many grams of need to be added to the beaker and then stir the solution. Cover it with plastic wrap and label with your names. YOU WILL KEEP THIS THE WHOLE WEEK! 1. Calculate the grams of needed to make 250 ml of a 0.25 M solution. 2. Calculate the ph of the solution: Procedure: Write a procedure in the space below. (# your steps) Include how much to add to how much water, how you will mix them, and how you will store your solution. (Read the top of the page for help) Instructor initials here before you begin. Store your covered base solution in the designated spot each day! 3

4 PART 2: % of acetic acid in Vinegar Purpose: Procedure: Titrate 10 ml of vinegar with your base solution (don t forget two drops of phenolphthalein!) to a light pink end point. Record the amount of used. Repeat until your volumes are within 0.5 ml. Trial Vinegar (L) Initial Final used used (L) Average Pre-lab Questions: 1. Determine the chemical formula of acetic acid. (Use PT) 2. Determine the molar mass of acetic acid. 3. Write out a balanced equation for the reaction between acetic acid and. Instructor initials before beginning 4

5 Post-lab Calculations: 1. What is the molarity of your base? 2. Determine the number of moles of base used in the titration. 3. Determine the number of moles of acid used in the titration. (mol ratio) 4. Calculate the molarity of the acetic acid in vinegar. (V=.01 L) 5. Use M = mol/l to determine how many moles of acetic acid are in 1 L of vinegar. 6. Calculate how many grams of acetic acid there would be in one liter of vinegar. 7. Assuming that one liter of vinegar has a mass of 1000 g, what % of the vinegar (by mass) is acetic acid? (grams acid) x 100%) Total mass 8. Assuming that the correct concentration by mass is 5% acetic acid, calculate your % error. (actual expt) x 100% actual 9. Write a concluding paragraph that discusses what you found for your % of acid in vinegar, % error and possible sources of error. 5

6 Part 3: Determine the concentration of H2SO4 Titrate 10 ml of the H2SO4 with your base solution (don t forget the indicator). Record the amount of used. Repeat until your volumes are within 0.5 ml. Purpose: Procedure: Trial H2SO4 (L) Initial Final Used used (L) Average Pre-Lab Questions: 1. Write out the neutralization reaction between and H2SO4. 2. What is the mole ratio of and H2SO4? Instructor initials before beginning 6

7 Post-Lab Questions: 1. What is the molarity of your base? 2. Calculate the moles of base used. 3. Determine the moles of acid. 4. Calculate the molarity of the acid. 5. Show Mrs. Benedict your molarity. Within: 0.03 = = 4 Score / = = = 1 6. Actual value = 7. Determine a % error based on the actual value. 8. Write a concluding paragraph describing what you found for the [H2SO4], your % error, and possible errors that could have occurred. 7

8 PART 4: Amount of acid in lemon juice. Purpose: Measure out 10 ml of lemon juice. Add 2 drops of phenolphthalein and titrate. (May be orange instead of pink) Record the amount of used. Repeat until your volumes are within 0.5 ml. Procedure: Trial lemon juice (L) Initial Final used used (L) Average Pre-lab Questions: 1. Determine the chemical formula of citric acid. (Use PT) 2. Determine the molar mass of citric acid. 3. Write out a balanced equation for the reaction between citric acid and. Instructor initials before beginning 8

9 Post-lab Calculations: 1. What is the molarity of your base? 2. Determine the number of moles of base used in the titration. 3. Determine the number of moles of acid used in the titration. (mol ratio) 4. Calculate the molarity of the citric acid in lemon juice. (V=.01 L) This is the experimental value. 5. The correct concentration of citric acid in lemon juice is 1.44 g/oz. Use the molar mass as a conversion factor to convert it to mol/oz g x oz 6. Continue with your answer to #5 (mol/oz) and use the conversion factor of oz in 1 Liter to convert it to mol/l. This is the actual molarity of the citric acid. 7. Calculate the % error for your citric acid concentration. (actual expt) x 100% actual 8. Write a concluding paragraph that discusses what you found for the [citric acid], your % error, and possible sources of error. 9

10 Review for the Titration Quiz: 1. Write out the chemical formulas for acetic acid, citric acid and sulfuric acid. Acetic acid Citric acid Sulfuric acid 2. Write out the neutralization reaction between hydrochloric acid and calcium hydroxide. 3. Which product from #2 is the salt? 4. If it takes 35.5 ml of 0.55 M HCl to neutralize 10.5 ml of the calcium hydroxide, what is the concentration (M) of the calcium hydroxide? (0.93 M) 5. Know the following words and what they are: phenolphthalein, buret, volumetric flask, titration, end point, indicator, meniscus, neutralization, and molarity. 10