Neutralization of acids and bases lab answers

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Pre-Lab Questions

1. What should you always wear to protect your eyes when you are in the chemistry laboratory?

Safety glasses or safety goggles should always be worn inside a chemistry lab to protect your eyes.

2. Should you add acid to water or water to acid?

Always add acid to water.

3. Where should you dispose of broken glass?

They should be placed in the proper container for the disposal of sharps. They should never be tossed into a regular trash can.

4. What should you do if you spill a chemical on your hand?

You should immediately wash your hands with copious amounts of water and antibacterial soap.

Exercise 1: What Is It?

A chemical laboratory contains special equipment to use while you are performing an experiment. Locate each of the items pictured on the following pages in your lab kit, and place a check mark in the appropriate place when you find it. After you have completed this, sketch a picture and name any additional items that are located in your lab kit, classroom, or home that are likely to be useful for you in completing these labs.

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Beaker

50 mL ____x_____

Stir Stick__x_______

250 mL ___x______ Graduated Cylinder

10 mL ____x_____

image9.png100 mL __x_______

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Test Tube ___x______ Pipette ___x______ Petri Dish ___x______

Include your Drawings Here:

Experiment 1: Neutralization of Acids and Bases

image12.jpgIn this experiment, you will learn how to properly neutralize and dispose of acidic and basic solutions.

Materials

5 mL 4.5% Acetic Acid (vinegar), C2H4O2 (1) 10 mL Graduated Cylinder 8 Litmus Test Strips (Neutral) Permanent Marker 2 Pipettes 1 g Sodium Bicarbonate (baking soda), NaHCO3

4 Weigh Boats *Water

*You Must Provide

Procedure

1. Use the permanent marker to label three of the weigh boats as A - C.

2. Measure and pour approximately 5 mL of water into weigh boat "A".

3. Add 0.5 g sodium bicarbonate to weigh boat "B".

4. Measure and pour approximately 5 mL of water into weigh boat "B". Gently pipette the solution up and down until the sodium bicarbonate is fully dissolved in the water.

5. Measure and pour 5 mL acetic acid solution to weigh boat "C".

6. Use the litmus test strips to determine if the substances in weigh boats A - C are acidic or basic. This is accomplished by briefly dipping an unused strip of the litmus paper in each of the weigh boats. Record your color results in Table 2.

7. Pipette 1 mL of the sodium bicarbonate solution from weigh boat "B" into weigh boat "C". Gently swirl weigh boat "C" to mix.

8. Develop and record a hypothesis regarding the pH of weigh boat “C”. Record this in the Post-Lab Questions section.

9. Test the pH of weigh boat "C" using new litmus paper. Record your result in Table 3.

10. Repeat Step 9 four more times until all the sodium bicarbonate has been added to weigh boat “C”.

Table 2: Initial Litmus Test Results

Weigh Boat

Chemical Contents

Litmus Results

Additional Observations

A

B

C

Table 3: Neutralization of an Acid

Amount of Base

Litmus Result

1 mL

2 mL

3 mL

4 mL

5 mL

Post-Lab Questions

1. State your hypothesis (developed in Step 8) here. Be sure to include what you think the pH will be, and why.

2. What is a neutralization reaction?

3. When might neutralization reactions be used in a laboratory setting?

4. At what point was the acetic acid in weigh boat “C” neutralized?

5. What do you think would have been the results if a stronger solution of sodium bicarbonate was used? Would it take more or less to neutralize the acid? What about a weaker concentration of sodium bicarbonate?

Pre-lab Questions

1. List the atomic numbers for each of the following elements.

Iron

_________

Oxygen

_________

Calcium

_________

Nitrogen

_________

Potassium

_________

Hydrogen

_________

2. What determines if a bond is polar?

3. Use the periodic table to determine if potassium chloride (KCl) formed through covalent or ionic bonds? Use evidence from the Introduction to support your answer.

4. Research two common, polar molecules and two common nonpolar molecules. Draw their molecular structure and explain how the structure makes each molecule polar or non-polar.

Experiment 1: Slime Time

image13.jpgInks can be polar or non-polar. Polar solvents pick up polar inks, while non-polar solvents pick up non-polar inks. In this experiment, you will use inks to identify slime and silly putty as polar or non-polar. You will also use paper chromatography to verify the inks are correctly identified as polar or non-polar.

Materials

(1) 250 mL Beaker 5 mL 4% Borax Solution, Na2B4O7·10H2O Dry Erase Marker (1) 10 mL Graduated Cylinder (1) 100 mL Graduated Cylinder Filter Paper (Disk) Filter Paper (Square) 0.5 g Guar Gum Highlighter Permanent Marker 1 Popsicle Stick

Silly Putty® Ruler Wooden Stir Stick Uni-ball® Roller Pen *Distilled or Tap Water *Newspaper *Notebook Paper *Scissors *You Must Provide

Procedure:

Part 1: Making Slime

1. Weigh out 0.5 g of guar gum into a 250 mL beaker.

2. Measure 50.0 mL of distilled water into a 100 mL graduated cylinder and pour it into the 250 mL beaker that contains the guar gum.

3. Rapidly stir the mixture with a wooden stir stick for three minutes, or until the guar gum is dissolved.

4. Measure 4.00 mL of a 4% Borax solution into a 10 mL graduated cylinder and add it to the guar gum and water.

5. Stir the solution until it becomes slime. This will take a few minutes. If the slime remains too runny, add an additional 1.0 mL of the 4.0% Borax solution and continue to stir until the slime is the slightly runny or gooey.

6. Once you are satisfied with the slime, pour it into your hands. Be sure not to drop any of it on to the floor.

7. Manipulate the slime in your hands. Write down observations made about how slime pours, stretches, breaks, etc. in Part 1 of the Data section. CAUTION: Slime is slippery and if dropped it can make the work area slick.

8. Place the slime back into the beaker and WASH YOUR HANDS.

Part 2: Slime and Putty Ink Tests

1. On a piece of notebook paper make one 20 - 25 mm long mark of each of the inks you are testing (permanent marker, highlighter, Dry Erase, and Uni-ball® Roller Pen). Space the marks at least one inch apart. Use a pencil to label each mark with its description.

a. Water soluble inks include those in highlighters and certain pens.

b. Water insoluble inks include those in a permanent pen/markers, newsprint, and a dry-erase markers.

2. While the inks are drying, select a passage or a picture in the newspaper to test with the slime.

3. Develop a hypothesis stating whether or not you believe the slime produced in Part 1 will pick up newsprint ink. Record this hypothesis in the Post-Lab Questions section. Then, break off a small piece of slime that is 3 - 5 cm in diameter. Gently place this piece on top of the newspaper print, then carefully pick it up again.

4. Observe and record in Table 1 whether or not the ink was picked up onto the slime.

5. Break off another small piece of slime. Once the inks from Step 1 have dried gently place the slime on top of the first spot on the notebook paper, then carefully pick it up. Repeat this for each of the inks. Observe and record which inks were picked up (dissolved) by the slime in Table 1.

6. Repeat this ink testing two more times for accuracy.

7. Hypothesize which inks the silly putty will pick up in the Part 2 of the Data section. Then, perform the ink tests with the Silly Putty® according to the procedure outlined in Steps 5 - 6.

Part 3: Chromatography of Ink Samples

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Figure 7: Chromatography apparatus for Procedure Part 3.

1. Use a pencil or scissors to poke a small hole in the center of a piece of filter paper (see Figure 7).

2. Spot the filter paper evenly spaced approximately 2 cm from the small hole with the two insoluble inks and the two soluble inks that were used in Part 2, Step 1.

3. Obtain a ½ piece of filter paper. Fold the paper in half several times so that it makes a narrow wick.

4. Insert the wick into the hole of the spotted paper so that it is above the top of the filter paper by approximately 2 cm.

5. Fill a 250 mL beaker ¾ full with water.

6. Set the filter paper on top of the beaker so that the bottom of the wick is in the water. The paper should hang over the edge of the beaker with the spotted side up.

7. Allow water to travel until it is approximately 1 cm from the edge of the filter paper. Remove the filter paper from the beaker.

8. Observe which inks moved from where they were originally spotted. Record your observations in Part 3 of the Data section.

Table 1: Results of Ink Testing for Silly Putty®

Name of Ink

Picked up (dissolved)

Did not pick up

Trial 1

Trial 2

Trial 3

Trial 1

Trial 2

Trial 3

Newsprint

Highlighter

Uni-ball® Roller Pen

Permanent Marker

Dry Erase Marker

Data

Part 1

· Slime Observations:

Part 2

· Hypothesis for Silly Putty® (Procedure Part 2, Step 7):

Part 3

· Observations of inks following chromatography:

Post-Lab Questions

1. Record your hypothesis regarding the slime’s ability to pick up newsprint ink here.

2. Did the slime pick up water soluble or water insoluble inks? From these results, what can you conclude about the polarity of slime molecules?

3. Explain how you determined your hypothesis about whether or not silly putty would pick up water soluble inks. Was your hypothesis correct?

4. Were the inks you used properly classified as soluble and insoluble? Explain your answer.

Pre-Lab Questions

1. Nitrogen fixation is a natural process by which inert or unreactive forms of nitrogen are transformed into usable nitrogen. Why is this process important to life?

2. Given what you have learned about the hydrogen bonding shared between nucleic acids in DNA, which pair is more stable under increasing heat: adenine and thymine, or cytosine and guanine? Explain why.

3. Which of the following is not an organic molecule; methane (CH4), fructose (C6H12O6), rosane (C20H36), or ammonia (NH3)? How do you know?

Experiment 1: Testing for Proteins

The protein molecules in many foods provide the amino acid building blocks required by our own cells to produce new proteins. To determine whether a sample contains protein, a reagent called Biuret solution is used. Biuret solution contains copper ions. However, the chemical state of the copper ions in Biuret solution causes them to form a chemical complex with the peptide bonds between amino acids (when present), changing the color of the solution. Biuret solution is normally blue, but changes to pink when short peptides are present and to violet when long polypeptides are present.

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Figure 6: Biuret solution only is located on the far left side of the image (blue). Note the transition from blue to violet as proteins are added to the solution, causing the solution to transition from blue to violet.

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(2) 250 mL Beakers 25 Drops Biuret Solution, H2NC(O)NHC(O)NH (1) Knox® Gelatin Packet 5 mL 1% Glucose Solution, C6H12O6 (1) 10 mL Graduated Cylinder (1) 100 mL Graduated Cylinder Permanent Marker 5 Pipettes

5 Test Tubes (Plastic) Test Tube Rack 5 mL Unknown Solution *Tap Water *Hot Water *Egg White *You Must Provide

Procedure

1. Label five test tubes 1, 2, 3, 4 and 5.

2. Prepare your testing samples as follows:

a. Mix one egg white with 25 mL water in a 250 mL beaker to create an albumin solution. Pipette 5 mL of this solution into Test Tube 1.

b. Mix the packet of Knox® gelatin with 50 mL hot water in a second 250 mL beaker. Stir until dissolved. Pipette 5 mL of this solution into Test Tube 2.

3. Pipette 5 mL of the 1% glucose solution into Test Tube 3.

4. Use the 10 mL graduated cylinder to measure and pour 5 mL of water into Test Tube 4.

5. Pipette 5 mL of the “Unknown Solution” into Test Tube 5.

6. Record the initial color of each sample in Table 1.

7. Develop a hypothesis regarding what you predict will happen when Biuret solution is added to Tubes 1 - 4. Record your hypothesis in the Post-Lab Question section. Then, pipette five drops of Biuret solution to each test tube (1 - 5). Swirl each tube to mix.

8. Record the final color in Table 1. Note: Protein is present in the sample if a light purple color is observed.

Table 1: Testing for Proteins Results

Sample

Initial Color

Final Color

Protein Present

1 - Albumin Solution

2 - Gelatin Solution

3 - Glucose

4 - Water

5 - Unknown

Post-Lab Questions

1. Record your hypothesis about what will happen when Biuret solution is mixed with the solutions from test tubes 1, 2, 3, and 4 here. Be sure to use scientific reasoning to support your hypothesis.

2. Write a statement to explain the molecular composition of the unknown solution based on the results obtained during testing with each reagent.

3. Diet and nutrition are closely linked to the study of biomolecules. How should you monitor your food intake to insure the cells in your body have the materials necessary to function?

4. The molecule pictured below produced a blue color when tested with Benedict’s reagent, a yellow color when tested with IKI, and a violet color when tested with Biuret reagent. Based on the structure shown below and these chemical results, what kind of biomolecule is this?

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