CHEM211 Lecture Notes - Pipette, Sample (Material), Significant Figures

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turquoisewalrus441

10 May 2018

School

University of Alberta

Department

Chemistry

Course

CHEM211

Professor

Charles Lucy

For unlimited access to Class Notes, a Class+ subscription is required.

Lab Practical Chem 211: Everything you need to know.

1. The lab practical consists of 8 buret readings → Your answer must be within plus or

minus 0.01 of the given value.

2. Aliquot Demonstration → Ensure to clean all glassware prior of use, and to wash three

times with solution before transferring.

a. Use a beaker (weight prior to adding mass) and add the solute to the beaker.

Calculate the mass to the closest 0.1 mg.

b. Add 20-30 mL of water to dissolve the solute.

c. Set up the funnel support, and rinse the funnel prior to use. Add a small (100mL)

volumetric flask and ensure the funnel is low within it.

d. Transfer solution with beaker touching the stirring rod. (Stirring rod needs to be

touching end of funnel).

e. Wash the beaker 3 times (minimum) to quantitatively transfer the solution into the

volumetric flask.Rotate and shake the beaker to dissolve/remove the solution

from the edges. After the beaker is clear of any solution (the rinse will become

clear if solution no longer in it). Wash the stirring rod and the funnel. Note that the

bottom of the funnel should also be cleaned.

f. After the volumetric flask is filled with ⅔ of the solution, swirl the volumetric flask

for 5 seconds to ensure solution is mixed well. Then, add remaining solution

CLOSE to the mark on the flask.

g. Wash an eye-dropper 3 times with water, then add solution until the bottom of the

meniscus is at the mark on the flask.

h. Stopper, Invert and Shake the volumetric flask 10 times.

i. Wash a clean beaker with the solution in volumetric flask three times. Then pour

some of solution in the beaker.

j. Add bulb to pipette, and make sure solution goes up so that you don’t cause

contamination when drawing some of solution in. Add about 2-3 mL, and turn

pipette horizontal to wash it with the solution. Wipe with kimwipe. Bring the

beaker to the pipette and tilt the beaker as you release the solution. Make sure

pipette is touching wall of beaker. Wash the pipette 3 times.

k. Draw solution into pipette and go over to the contaminated beaker and adjust the

meniscus. Do NOT do this in the original solution, you will contaminate it! After

meniscus is adjusted, place solution in 250mL volumetric flask. (If you use a

funnel to send pipetted solution into flask make sure to wash funnel with distilled

water 3 times beforehand! BUT, I don’t think that's what is required. Verify.)

l. Add water until before the mark, then use dropper to adjust!

3. Significant Figures → Have a clear understanding of Significant figures as you will be

required to calculate and determine the significant figures on the Lab Practical Exam!

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Document Summary

Calculate the mass to the closest 0. 1 mg: add 20-30 ml of water to dissolve the solute, set up the funnel support, and rinse the funnel prior to use. After the beaker is clear of any solution (the rinse will become clear if solution no longer in it). Note that the bottom of the funnel should also be cleaned: after the volumetric flask is filled with of the solution, swirl the volumetric flask for 5 seconds to ensure solution is mixed well. Then pour some of solution in the beaker: add bulb to pipette, and make sure solution goes up so that you don"t cause contamination when drawing some of solution in. Add about 2-3 ml, and turn pipette horizontal to wash it with the solution. Bring the beaker to the pipette and tilt the beaker as you release the solution. Make sure pipette is touching wall of beaker.

Related Questions

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.

Miniscale nitration of methyl benzoate was performed in the lab:

Procedure below:

1. Prepare and ice bath in a 100mL beaker on a magnetic stir plate.

2. To a clean, dry 25 mL Erlenmeyer flask, add 1.0 mL of methyl benzoate via pipet.

3. Calculate the mass of methyl benzoate.

4. To the methyl benzoate, add 2.25 mL of concentrated (18M) sulfuric acid and a spin bar.

5. Carefully clamp the flask so that it is immersed in the ice bath and begin stirring.

6. Prepare the nitrating solution by adding 0.75mL of concentrated (18M) sulfuric acid and 0.75mL of concentrated (16M) nitric acid to a clean, dry vial.

7. Cool the mixture in a second ice bath.

8. With a Pasteur pipet, slowly add the cooled sulfuric acid-nitric acid solution to the stirred solution of methyl benzoate. *Addition should take approximately 15 minutes. Adding the nitrating agent more rapidly will increase the amount of by-products and decrease the yield

9. After all of the nitrating agent has been added, carefully remove the ice bath.

10. Continue stirring until the reaction has come to room temperature.

11. Then let the reaction flask stand undisturbed for 15 minutes.

12. Place 10 g of ice in a 100mL beaker.

13. With a Pasteur pipet, carefully transfer the reaction mixture to the beaker.

14. Rinse the flask with 5mL of cold water.

15. When the ice has melted, vacuum filter the crude crystals using a Buchner funnel.

16. Wash the crystals with 2 5mL portions of cold water and finally with 2 1.5mL of cold methanol.

17. The crude product can be recrystallized from methanol.

18. Record the mass of the dry product and calculate the yield.

QUESTION: What is the major product formed in this reaction? Justify your reasoning..

I am so confused! Appreciate the help and thank you
Average mass of Pepto bismol tablets - 1.021
Mass in weighing boat = 10.080 g
Mass of emptied weighing boat = .003
subtract the two masses = 10.077
Measured mass of 2nd filter paper 0.116G
Watch glass 54.756

Obtain 10 pepto bismol tablets. Find the average mass of the 10 tablets and calculate the average mass/tablet. Average mass of pepto bismol tablet = 1.021

Grind the tablets

Pour the contents into a weighing boat and find it mass. 10.080 g

Pour the contents of the weighing boat in a 250 ml beaker and find the mass of the weighing boat after it is emptied. Subtract the two masses for the mass of the ground tablets in the beaker. Mass of emptied weighing boat = .003 subtract the two masses = 10.077

Measure 100 ml of 2 M HCI into a graduated cylinder.

Add 20 ml of 2 M HCI to the powder and mix with a glass rod until it stops foaming.

Using a Buchner funnel, filter paper and a clean arm flash that has been rinsed with purified water, filter the the solution.

if the filtrate is cloudy, pour it back into the beaker and filter it through the same piece of filter paper again.

using your squeeze bottle, rinse the beaker with small amounts of purified water and pour into the funnel. This rinses the solids in the process.

Transfer the solution to 250mL to a volumetric flask.

Use a 25ml volumetric pipette to measure 50 ml of your solution into a beaker.

Measure 60 mL of 0.2 M Na3PO3 in a graduated cylinder and add to the beaker.

using a buchner funnel, filter paper and side arm flask, filter the solution and retain the solid. Filter this solution until clear.

Once your BiPO4 has been filtered, place the filter paper onto a pre weighed watch glass and place it where instructed to dry until next week.

The following week, obtain the mass of the BiPo4 precipitate.

1 Calculate the mass of pepto bismol tablets that were placed into your beaker in step 4 week 1
2 calculate the mass of dry BiPO4 precipitate by subtracting the watch glass and filter paper mass.
from the mass of precipitate, calculate moles of BiPO4 that were formed.
3 Using the moles found in (3) and the knowledge that each sample used 50 ml of solution find the concentration in moles/L of Bi3+ in solution before you added Na3PO4.
4 With the concentration calculated in (4) calculate the total number of moles of Bi in the 250 ml volumetric flask.
5 Knowing that each Bismuth subsalicylate molecule contains 1 bismuth atom (a 1:1 ratio), calculate the number of moles of bismuth subsalicylate you added to your original beaker and convert this to grams.
6 Divide grams of bismuth subsalicylate (6) by grams of pepto bismol used (1). This will give you an answer in units of g Bi-SS/g PB tablet.
7 Knowing your average mass per tablet, find the mass of Bi-SS tablet. Hint you have g Bi-SS g PB and you have g PB tablet.

CHEM211 Lecture Notes - Pipette, Sample (Material), Significant Figures

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