Chemistry Homework-Polar Bonding

Lab 7: Polar Bonding

Pre-lab Questions

1. What two conditions are considered when determining whether a molecule is polar or non-polar?

2. What determines if a bond is polar?

3. List several examples of polar molecules.

4. List several examples of non-polar molecules.

5. What is the rule when using polar and non-polar solvents?

Experiment: Slime Time

Some inks are polar while others are non‐polar. A polar solvent will pick up polar inks, while a non‐polar solvent will pick up non‐polar inks. In this lab 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.

Procedure

**Take photographs of your experiment for Parts 1, 2, and 3; and your results. Submit them with your laboratory report.**

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 stirring rod for at least 3 minutes and 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 right consistency.

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.

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. 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 permanent pens/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. Break off a small piece of slime that is 3 – 5 cm in diameter. Gently place this piece on top of the newspaper print, and 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, and 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. Before performing ink tests on silly putty, in the Data section, hypothesize which inks the silly putty will pick up.

8. Perform ink tests on silly putty in the same manner as above. Record your results in Table 2

Part 3: Chromatography of Ink Samples

1. Use a pencil or scissors to poke a small hole in the center of a piece of filter paper (see Figure 4).

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.

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 3/4 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.

Data

Part 1

· Slime Observations:

Part 2

Table 1: Results of Ink Testing for Slime

Name of InkPicked up (dissolved)Did not pick up
Test 1Test 2Test 3Test 1Test 2Test 3
Newsprint   
Highlighter      
Roller ball pen      
Sharpie marker      
Dry-erase marker      

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

Table 2: Results of Ink Testing for Silly Putty

Name of InkPicked up (dissolved)Did not pick up
Test 1Test 2Test 3Test 1Test 2Test 3
Newsprint   
Highlighter      
Roller ball pen      
Sharpie marker      
Dry-erase marker      

Part 3

· Observations of inks following chromatography:

Post-lab Questions

1. Take photographs of your experimental set up for Parts 1, 2, and 3 and your results. Submit them with your laboratory report.

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. Was your hypothesis correct?

4. Were the inks you used properly classified as soluble and insoluble? Use evidence from your results to explain your answer.

Lab 8: Chemical Reactions I

Pre-lab Questions

1. Name the chemical that makes up teeth.

2. How does plaque harm teeth?

3. How does fluoride promote dental health?

4. Write two solubility rules that are used in this lab.

Experiment: Battle of the Mouth Rinses

Some mouth rinses contain fluoride, usually in the form of sodium fluoride, which is soluble in water. In this lab, you will determine which one of two mouth rinses would be better at preventing cavities by replacing lost minerals with fluoride. You will do this by determining which rinse contains fluoride.

Procedure

**Take photographs of your experiment set up and your results. Submit them with your laboratory report.**

1. Label the two test tubes with a permanent marker as A and B.

HINT: Make sure to write down which rinse is A and which is B.

2. Pour 10 mL of Rinse A into the test tube marked A.

3. Pour 10 mL of Rinse B into the test tube marked B.

HINT: If using the same graduated cylinder to measure your rinses, wash the cylinders WELL between pours to prevent cross-contamination.

4. Pour 3 mL of 1 M Ca(C2H3O2)2 solution into each of the test tubes. Gently stir each test tube with a stir rod to mix. Be sure to clean your stir rod each time before placing it in a solution.

CAUTION: Mixing should be done gently to prevent glass breakage and injury.

5. Observe and record initial observations immediately after adding calcium acetate to the test tubes.

6. Observe the reactions for at least 10 minutes to ensure it is finished. HINT: A positive test is indicated by a cloudy appearance of the solution. The precipitate formed can be more easily seen if the test tube is held up to the light. The precipitate will eventually settle to the bottom of the test tube.

7. Let the test tubes sit for an hour. After an hour, record final observations.

8. Record all observations in the Data section.

9. To clean up, you can rinse the small amount of precipitate down the drain.

Data

· Observations of NaF and Ca(C2H3O2)2 (see sequence of pictures below)

· Observations of Rinse A and Ca(C2H3O2)2

· Observations of Rinse B and Ca(C2H3O2)2

Post-lab Questions

1. Take photographs of your experiment set up and your results. Submit them with your laboratory report.

2. Did either of the mouth rinses contain fluoride? How did you know?

3. Which mouth rinse would be better at fighting cavities? Why?

4. Based on the solubility rules learned in this lab, could you use potassium nitrate to test for fluoride in mouth rinses? Explain your answer.

Lab 9: Chemical Reactions II

Pre-lab Questions

1. Michelangelo used fresco painting when he painted the Sistine Chapel. Fresco painting involves most of the types of chemical reactions you just studied. Listed below are some of the reactions used in creating a Fresco painting. Identify the type of chemical reaction used for each step and balance the chemical equation if needed.

Initially, some sort of heat must be generated. Propane is an example of a common fuel source used for heating.

C3H8 + O2 → CO2 + H2O

This is a ____________________________________________ reaction.

Next, quicklime (calcium oxide) is made by roasting calcium carbonate (limestone).

CaCO3 → CaO + CO2

This is a ____________________________________________ reaction.

The quicklime is slaked to form lime plaster.

CaO + H2O → Ca(OH)2

This is a ____________________________________________reaction.

The lime plaster is cured or dried.

Ca(OH)2 + CO2 → Ca(OH)(HCO3)

This is a ____________________________________________ reaction.

This quickly continues to react to form calcium carbonate and water.

Ca(OH)(HCO3) → CaCO3 + H2O

This is a ____________________________________________ reaction.

Frescos will deteriorate over time when exposed to the damp, acidic environments typical of modern urban city atmospheres.

CaCO3 + H2SO4 → CaSO4 + H2O + CO2

This is a ____________________________________________ reaction.

2. Balance each of the chemical equa_ons you will be doing in this laboratory exercise.

Combustion:

C4H10 (g) + O2 (g) → CO2 (g) + H2O(g)

Synthesis:

Hb (s) + O2 → HbO2 (s)

Single Replacement:

Zn (s) + H3C6H5O7 (aq) → Zn3(H3C6H5O7)2 (aq) + H2 (g)

Double Replacement:

Zn(C2H3O2)2 (aq) + Na3PO4 (aq) → NaC2H3O2 (aq) + Zn3(PO4)2 (s)

Decomposition:

(NH4)2CO3 (s) → NH3 + H2O + CO2 (g)

Experiment: Getting to Know your Reactions

Procedure

**Take photographs of your experiment set up for Parts 1 – 5 and your results. Submit them with your laboratory report.**

Part 1: Combustion

C4H10 (g) + O2(g) → CO2 (g) + H2O (g)

1. Light a butane lighter and observe the flame. (The ignition of the flame is a reaction between butane and the oxygen in the air you breathe.)

2. Record your observations in the data table from when the lighter is turned on until it is turned off.

Part 2: Synthesis (A + B → C)

Hb(s) + O2 → HbO2 (s)

1. Take a deep breath, hold it as long as possible and then exhale. Visualize the reaction occurring.

2. Record your observations before inhaling and a>er you exhale.

3. Construct an oxyhemoglobin molecule with modeling clay and toothpicks.

Hint: See figure of molecule in introduction as a guide.

4. Take a photograph of your model and submit it with your laboratory report.

Part 3: Single Replacement (A + BC → AC + B)

Zn (s) + H3C6H5O7 (aq) → Zn3(C6H5O7)2 (aq) + H2 (g)

1. Place a test tube in a test tube rack or small beaker.

2. Slightly tilt a test tube and slide a small zinc-coated (galvanized) washer down the side.

3. Use a 10 mL graduated cylinder to measure out approximately 2 mL of saturated citric acid and carefully pour it into the test tube containing the zinc washer.

CAUTION: Citric acid is irritating to the eyes and skin.

4. Observe the reaction for several minutes, and record your observations in the data table.

5. To clean up, separate the acid solution from the washer by pouring it into a small beaker while leaving the washer in the test tube. This is called decanting. Rinse the test tube containing the washer several times with water and add each rinse to the beaker.

CAUTION: Do not pour the acid directly down the drain. To neutralize the acid, add small amounts of baking soda to the solution in the beaker and stir with a stirring rod.

6. Continue stirring and adding small amounts of baking soda until gas no longer forms. Pour the liquid down the drain and throw the washer in the trash.

Part 4: Double Replacement (AB + CD → CB + AD)

Zn(C2H3O2)2 (aq) + Na3PO4 (aq) → NaC2H3O2 (aq) + Zn3(PO4)2 (s)

1. Pour approximately 2 mL of 0.1 M zinc acetate (Zn(C2H3O2)2) into a clean test tube.

2. Add approximately 2 mL of 0.1 M sodium phosphate tribasic (Na3PO4) into the test tube.

3. Record your observations before and after the addition of Na3PO4 in the data table.

4. To clean up, pour the contents of the test tube down the drain.

Part 5: Decomposition (AB → A + B)

(NH4)2CO3 (s) → NH3 + H2O + CO2 (g)

1. Place a spatula tip full (approximately 0.02 g) of ammonium carbonate (NH4)2CO3, powder into a test tube.

CAUTION: Do not inhale the strong ammonia odor. Try to work in well-ventilated area.

2. Light the candle using the butane lighter.

CAUTION: Long hair should be tied up and loose clothing restrained when around an open flame to prevent fire and burns. Be sure you are wearing your safety goggles.

3. Use a test tube holder to hold the test tube containing the ammonium carbonate at a slight angle in the candle flame. Keep the open end of the tube pointed away from you and other students. Continue to heat the sample until the reaction is finished.

Hint: Remember the products of this reaction are all gases.

4. Record your observations in the Data section.

5. Allow the test tube to cool to room temperature before touching it.

CAUTION: The test tube will be very hot and can burn your skin if touched before it cools.

Hint: After the test tube has cooled for a few seconds, place it in a small beaker or test tube rack to finish cooling.

6. Extinguish the candle. Wash out the test tube with soap and water.

Data

Table 1: Reaction Observations, Parts 1-5

SubstanceBefore the ReactionAfter the Reaction
Combustion
Synthesis
Single Replacement
Double Replacement
Decomposition

Post-lab Questions

1. Take photographs of your experiment set up for Parts 1-5, including the oxyhemoglobin molecular model from Part 2: Synthesis. Submit them with your laboratory report.

2. Write the combustion reaction that occurs when you cook out on a propane gas grill. Propane has the chemical formula C3H8. Make sure to balance the reaction equation.

3. Balance the following equations and identify the type of reaction.

a. BaCl2 (s) + K2SO4 (aq) → BaSO4 (s) + KCl (aq)

b. KClO3 (s) → KCl (s) + O2(g)

c. H2 (g) + O2 (g) → H2O (l)

d. F2 (g) + LiCl (aq) → LiF (aq) + Cl2 (l)

Lab 9: Chemical Reactions II

Pre-lab Questions

1. What is a limiting reagent?

2. A student used 7.15 g of CaCl2 and 9.25 g of K2CO3 to make CaCO3. The actual yield was 6.15 g of CaCO3. Calculate the limiting reagent and the percent yield.

Experiment: Synthesis of Garden Lime

Procedure

**Take photographs of your experiment set up and your results. Submit them with your laboratory report.**

1. Table 1 provides an example set of data for 1.0 g CaCl2.

2. For Trial 1, weigh into a 250 mL beaker the amount of calcium chloride (CaCl2) shown in Table 1. Record the exact mass you weigh out in the Trial 1 column of the Data section.

3. Measure 50.0 mL of distilled water into a 100 mL graduated cylinder. Pour the water into the 250 mL beaker with the calcium chloride.

4. Stir the solution with a stirring rod until all of the calcium chloride is dissolved.

5. Weigh out 2.5 g of potassium carbonate (K2CO3) in a 50 mL beaker. Record the exact mass in the Data section.

6. Measure 25.0 mL of distilled water into a 100 mL graduated cylinder. Add the water into the 50 mL beaker containing the potassium carbonate.

7. Stir the potassium carbonate in the distilled water with a stirring rod until it is all dissolved.

8. Pour the K2CO3 solution into the 250 mL beaker that has the CaCl2 solution. Rinse the beaker that contained the K2CO3 with a few mL of water and add this to the CaCl2 solution. Stir the mixture.

9. As soon as the reaction begins, record your observations in the Data section. Continue stirring until you see no more precipitate forming.

10. Set up the funnel in the Erlenmeyer flask as shown in Figure 2.

HINT: Do NOT begin filtering yet!

11. Zero the scale and weigh a piece of filter paper and a watch glass. Record the masses of both items in the Data section.

12. Prepare a filtering funnel as shown in Figure 2: fold a piece of filter paper in half twice to make quarters, and open the paper to make a small cone (three quarters are open on one side and one quarter is on the opposite side). Place the paper cone into the funnel and hold it in place with your fingers. Pour a small amount of distilled water through the paper to secure it inside the funnel.

13. Filter the mixture by pouring it into the filter paper in the funnel. Use the stirring rod and distilled water in a wash bottle to transfer the entire solid into the filter paper.

HINT: For best results, be sure to transfer all of the precipitate into the filter paper. Use a rubber policeman if it is available to help with the transfer.

14. Rinse the remaining solid in the filter paper twice with distilled water from a wash bottle to rinse off excess sodium chloride (NaCl). After all the liquid has filtered through, rinse the product with approximately 5 mL of ethanol to aid in its drying. Allow the ethanol to completely finish filtering through the paper.

15. Remove the filter paper carefully so as to not lose any product. Gently unfold the filter paper and lay it flat on the pre-weighed watch glass to dry.

16. Allow the product to air dry completely. This may take 24 hours or more. Once dry, weigh the dry product on the filter paper and watch glass. Record the total mass in the Data section. Calculate the mass of the product.

17. Repeat the above procedure for Trial 2 using the amount of CaCl2 mass indicated in Table 1.

18. To clean up, wash any dirty glassware, pour liquids down the drain, and throw the product on the filter paper in the trash.

Data

1. Record your data for each of the trials in Table 2.

2. Record your reaction observations (Step 8) below:

Table 2: Reaction Product Data

Mass (g)ExampleTrial 1Trial 2
Mass of CaCl21.0 g
Mass of K2CO32.5 g
Mass of filter paper0.8 g
Mass of watch glass38.5 g
Combined mass of product, filter paper, and watch glass40.2 g
Mass of dry product0.9 g

Calculations

1. Determine the limiting reagent for each trial. Show your calculations.

Hint: See the example in the Introduction.

Example:

Trial 1:

Note: These should be about the same and either CaCl2 or K2CO3 can be the limiting reagent depending on their initial masses.

Trial 2:

Table 4: Comparison of Theoretical and Actual Yields for CaCO3

Trial #Limiting ReagentTheoretical Yield of CaCO3Actual Yield of CaCO3% Yield
Trial 1
Trial 2
Trial 3

2. Calculate the theoretical yield of CaCO3 that could be produced by each trial and then fill in Table 2.

3. Find the percent yield each trial obtained for the CaCO3.

Post-lab Questions

1. Take photographs of your experiment set up and you results. Submit them with your laboratory report.

2. Compare the results of the different trials. How does the amount of grams of CaCO3 compare?

3. Were the results of the trials as you expected? Why or why not?

4. Predict what would happen if 6.0 grams of CaCl2 were used for the reaction and the amount of K2CO3 remained the same.

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