CHEM 101 Study Guide - Graduated Cylinder

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blushbadger787

17 Nov 2014

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Purpose: the purpose of this lab is to measure the mass and volume of pennies to determine the density of pennies, and to interpret the class data to determine approximately when the composition of pennies changed. Hypothesis: if i measure the density of pennies from different years, then it will be possible to track changes in the composition of the penny. Materials: the materials in this lab are: 10 pennies of varying mint dates, balance sensitive to 0. 01 g, 50-ml graduated cylinder having 1-ml graduations. Procedure: record the mint date of each penny in the data table, weigh each penny and record the mass to the nearest 0. 01 g, run tap water into the graduated cylinder until it is approximately one-half full. Read and record the volume to the nearest 0. 1 ml: carefully add the 10 pennies to the cylinder so that no water splashes out. Jiggle the cylinder to dislodge any trapped air bubbles.

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You will need: seven kinds of plastic containers with different recycle codes, scissors, two cups or beakers, two stirring rods or wooden craft sticks, room temperature water, 70% isopropyl alcohol, graduated cylinder, acetone, 2 plastic pipets, hot plate with a 400 mL beaker of boiling water (student groups may share the boiling water), tongs, and forceps.

Cut a small, flat piece (1.5 cm Â´ 1.5 cm) from each container (seven total) and start a data table to record the color and shape of each piece as well as the permanent marker letter label (AâG) your instructor previously marked on each container. If two containers are the same color, cut different shapes (triangle, rectangle, circle, etc.) to help with piece identification. Now you are ready to follow the flowchart. Record your observations in the data table as you go along.

Tap Water Test: Place all seven pieces of plastic in a beaker or cup of room temperature tap water. Stir vigorously with a stirring rod or wooden craft stick to dislodge any bubbles from the plastic pieces. Bubbles tend to adhere to plastics. How would this change the apparent density? Observe and record which pieces sink and which float.

70% Alcohol Test: Remove the pieces that float from the water. Add them to a beaker or cup containing about 20 mL of 70% isopropyl alcohol. Stir. Do the pieces sink or float in the 70% alcohol? How does the density of alcohol compare to water?

Using a plastic pipet, add a squirt of tap water to the beaker containing alcohol. Stir. Do any of the pieces begin to float? When adding water to 70% alcohol, how does the density of the solution change? Keep adding squirts of water and stir until one piece floats. According to the flowchart, what is the identity of this plastic? Remove the piece and record your results.

Add more squirts of water until a second piece floats. Remove the piece and record the identity of the second plastic. You can now identify the third piece since it is still sinking.

Boiling Water Test: Place the four pieces that sank in tap water in the beaker of boiling water for a minimum of 30 s. Using tongs, remove them one at a time and test their flexibility, noting their size and color. Record your results. Which plastics can you now identify using the flowchart?

Acetone Test: Place the final two plastic samples in a small amount of acetone for one minute. Record your results.

Check with your instructor to see whether you correctly identified the seven plastics. You are now ready for an unknown. If your unknown floats in the tap water test, you will need to use the known pieces for PP, HDPE, and LDPE along with your unknown to help you with the identification in the 70% alcohol test.

Table 1. Selected Physical Properties of Common Plastics
Number	Plastic Type and Composition	Density, g/mL	Glass Transition Temperature, Â°C	Melting Temperature, Â°C
1	PET or PETE: poly(ethylene terephthalate)	1.38â1.39	60â85	250â265
2	HDPE: high-density polyethylene	0.95â0.97	~ â125	~138
3	PVC or V-poly(vinyl chloride)	1.16â1.35	81â98	200â300
4	LDPE: low-density polyethylene	0.92â0.94	â128 to â30	~138
5	PP: polypropylene (isotactic when all methyl groups are on the same side of the chain)	0.90â0.91	â8	174â177
6	PS: polystyrene	1.05â1.07	80â100	240
7	PLA: polylactic acid (d and l conformations cause numbers to differ)	1.25â1.26	50â80	173â178

Fill out the following table:

Letter Label	Sampleâs Color	Sampleâs Shape	Floats in Water? (Yes/No)	Sinkersâ Boiling Water Results (Note color/shape changes.)	Sinkersâ Acetone Test Results (Note texture changes.)	Floatersâ Alcohol Test Results (Note number of squirts.)	Plastic Type
A
B
C
D
E
F
G

PROCEDURE Safety Precautions: Sodium hydroxide and Acids are corros and will damage your skin and eyes. To perform the experiment, a pH sensor will be placed in the acid solution. The pH sensor is used to monitor pH as the titration with sodium hydroxide is performed Record the pH values and corresponding volume (mL) of NaOH added. Enough data points will have to be generated to obtain a smooth curve. In some regions of the titration, the pH will change very slowly, and larger increments of base, mL, can be added. Near the equivalence point (before and after), the pH changes very quickly, and the NaOH should be added dropwise. The subsequent pH reading should be recorded after the addition of each quantity of NaOH. The titration setup is shown in Figure 3. Center the beaker and the stir-bar on the stir-plate. Clamp the pH probe such that the tip and ball are submerged below the surface of the solution but, not touching the bottom. Allow sufficient clearance to allow the stir bar to spin freely 1. 150 mL beakers can be used to transport reagents from standardized bottles. This will avoid cross- contamination of the standardized bottles Obtain approximately 15 mL of the standardized hydrochloric acid, solution, approximately 15 mL of the standardized acetic acid solution, and approximately 75 mL of the standardized sodium hydroxide solution in separate beakers. Use the lab tape and markers to label beakers. Beakers should be covered with a watch glass when they're not in use 2. Record the concentrations of the HCI, CH3COOH, and NaOH solutions, which are on the reagent bottles, in the laboratory notebook. 3. Obtain a magnetic stir plate and a ring stand with a burette clamp and a small 3-finger clamp Figure 3. Titration setup 4. Clean and rinse a 25 mL burette. This burette will be used to dispense the NaOH. The lab team should discuss and decide on the appropriate material to use for the final rinse. If air bubbles appear in the tip of the burette, aggressively tap the burette to dislodge the bubbles. If bubbles continuously reappear then the burette has a small leak and the valves need to be serviced (discuss this with the lab instructor). TITRATION OF HCL 5. Measure 100.0 mL of DI water with a 100.0 mL graduated cylinder and pour it into a 250 mL beaker. Use a pipette to add 10.00 mL of the standardized acid solution into the same 250 mL beaker and add 2-3 drops of phenolphthalein indicator. Place the Teflon Stir Bar in the beaker carefully. General Chemistry 2

Calculations First Trial UPDATED

Theoretical yield (CaCO3):

Actual yield (CaCO3):

Percent yield:

Moles of Ca present in original solution, based on actual yield:

Mass of CaCl2 present in original solution, based on actual yield:

Can someone please help me with these three easy questions please? Thank you! SHOW ALL WORK!!

THIS IS MY DATA FROM MY LAB EXPERIMENT. I JUST NEED FOR YOU TO FIND THE ANSWERS TO THE ABOVE QUESTIONS WITH WORK SHOWN!

Table 1: Data and Observations
	Mass
CaCl₂ :	ORGINAL MASS: 2.0g AFTER 24 HOURS 5.8g
K₂CO₃ :	2.5g
Filter Paper	2.1 g
Watch Glass	33.6g
Precipitate	3.3g

Procedure

Put on your safety glasses and gloves (provided in your safety box).

Turn on the scale by pressing the button labeled "0/T". If your scale does not turn on, you may have to remove the battery cover and remove a small strip of plastic from the battery housing. Once the scale is on, press the "0/T" button a second time to zero the scale. Make sure that the units are in grams (g). If not, press the M button until the units displayed are in grams.

Place a weigh boat on the scale and record the mass in Table 2. Zero the mass of the weigh boat by pressing the "0/T" button. Your scale should now read 0 g.

Add 2.0 g of CaCl₂ to the weigh boat. Record the mass in Table 2. Set this sample aside, and let it sit exposed to the air (but otherwise undisturbed) for 24 hours. Complete Steps 3 - 23 while you wait.

Place a 250 mL beaker on the scale and zero it.

Add 2.0 g of CaCl₂ to the beaker. Record the exact mass of the powder in Table 1.

Remove the beaker from the scale. Use a 100 mL graduated cylinder to measure and pour 50 mL of distilled water into the beaker and mix with the stir rod until all the CaCl₂ has dissolved.
Note: This is an exothermic process, so the beaker may become warm.

Place a 50 mL beaker on the scale and zero the scale.

Add 2.5 g of K₂CO₃ to the 50 mL beaker. Record the exact mass of the powder in Table 1.

Remove the beaker from the scale. Use the 100 mL graduated cylinder to measure and pour 25 mL of distilled water into the 50 mL beaker. Mix with the stir rod until all the K₂CO₃ has dissolved.

Rinse the stir rod with water.

Add all of the K₂CO₃ solution to the beaker containing the CaCl₂ solution. It is important that all of the K₂CO₃ is added to the beaker. To ensure this, rinse the 50 mL beaker with up to 5 mL distilled water, and pour the rinse in the CaCl₂ solution.

Using the stopwatch to keep time, stir the solution with the stir rod for four minutes. Then, allow it to sit for 15 minutes. This will allow sufficient time for the chemical reaction to occur.

Rinse the stir rod with water.

Place a piece of filter paper on the scale and record the mass in Table 1.

Place a watch glass on the scale and record the mass in Table 1.

Fold the filter paper in half and in half again so that it resembles a triangle with one arched side.

Pull apart one fold of the filter paper so that three sides of the filter paper remain together, with one side making up the other half of the funnel shape (Figure 5).

Hold the funnel over a sink or any sized container. Place the paper into the funnel and use a pipette to drip 5 mL of distilled water around the edges of the filter paper. This will prevent the filter paper from rising up out of the funnel.

Rest the funnel on top of the Erlenmeyer flask.

After 15 minutes has passed, swirl the beaker and slowly filter the solution (that you created in Step 9) from the 250 mL beaker through the filter paper. Additional distilled water may also be used to transfer any remaining solid into the filtration apparatus.

After all the solution has been filtered, use the pipette to rinse the filter paper with approximately 5 mL of isopropyl alcohol to aid the drying process. Allow the isopropyl alcohol to completely drip through the filter before removing filter paper from the funnel.

Carefully remove the filter paper. Unfold and place it precipitate-side up onto the pre-weighed watch glass. Be sure not to lose any precipitate during this transfer.

Allow the precipitate to dry, undisturbed, for at least 24 hours. Determine the mass of the product recovered by re-weighing the system and subtracting the weight of the filter paper and watch glass. Record your data in Table 1.

Re-weigh the sample of CaCl₂ that was allowed to sit exposed for 24 hours. Subtract the mass of the weigh boat and record the mass and your observations in Table 2.

TABLE 2 IS NOT IMPORTANT IN SOLVING THE QUESTION AS IT JUST ASKS FOR MY OBERVATION OF CaCl₂ AFTER 24 HOURS. ALSO TO FIND THE ACTUAL YIELD, YOU WOULD HAVE TO FIND FIRST THE PERCENT YIELD AND THEORTICAL YIELD.

CHEM 101 Study Guide - Graduated Cylinder

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