CHEN 3701 Lecture Notes - Lecture 25: Reaction Rate Constant, Spatial Gradient
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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.
1-How many grams of NaCl would be needed to prepare 150.00 L of a 1.402 M NaCl solution?
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2- first a standardized solution of sodium hydroxide (NaOH) will be quantitatively diluted to about 0.1 M but not exactly 0.1M. The molarity of the dilute NaOH will be calculated! A similar quantitative dilution was done in experiment 3 when you diluted 5.0 M HCl to 0.50M HCl using a volumetric flask and pipet.
The second part of the experiment is very similar to the last part of experiment 6 where samples of the unknown were weighed out, dissolved in water, and titrated with the dilute NaOH using phenolphthalein as the indicator to determine the percent by mass of a compound in the unknown. The compound will be different than the compound used in experiment 6. The molecular formula of the compound will be provided during the final. You must know how to weigh by difference (Preweigh, tare sample and small container to zero, transfer sample to flask, and place the small container back on balance to get mass) and titrate the sample using the buret in order to do well.
Be sure to read the instructions for the practical toward the end the CHM151L lab manual and do the practice problem on the next page.
You will have 1.5 hours to do the practical. You may only use a calculator and a pencil on the practical. There is no talking during the practical such that students cannot help each other and the TA may only help you with equipment problems.
It would be a good idea to wash any glassware you might use the lab period before the lab practical. There will also be a help session before the lab practical.
At the end of the lab final you will wash all glassware used or any dirty glassware in your locker, wash your unknown vials and remove the labels, checkin your locker and return your key, and evaluate the lab.
Please put the following statements in the correct order relating to the day of the lab practical:
1 2 3 4 5 6 Wash all your glassware and unknown vials, checkin your locker, evaluate the lab, and check your grades.
1 2 3 4 5 6 Do at least 3 good trials (weigh and titrate sample) as time allows.
1 2 3 4 5 6 Start the lab practical by diluting the NaOH solution.
1 2 3 4 5 6 Before the day of the practical clean glassware, read the practical instructions and do the practice problem in the lab manual and complete the loncapa problems for the final.
1 2 3 4 5 6 Calculate the molarity of the dilute NaOH, the percent by mass of the compound in you unknown for each trial and then the median.
1 2 3 4 5 6 Come to the help session before the lab final.
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3-
A NaOH solution was prepared by diluting 5.00 mL of 2.205 M NaOH to a final total volume of 100.00 mL. What is the exact molarity of the dilute NaOH (use 4-5 significant figures)?
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4-For the problem above, select glassware and size from the list below to conduct the dilution.
| A | Amber Bottle |
| B | Mohr pipet |
| C | Buret |
| D | Volumetric Flask |
| E | Volumetric Pipet or Pipettor |
| F | Graduated cylinder |
| G | Erlenmeyer flask |
| H | Beaker |
A B C D E F G H <= Glassware used to transfer the 2.205 M NaOH to be diluted
A B C D E F G H <= Glassware used to measure the final volume of the diluted M NaOH.
5 10 15 20 25 50 100 250 500 1000 <= Volume of the glassware chosen to transfer the concentrated NaOH above
5 10 15 20 25 50 100 250 500 1000 <= Volume of the glassware chosen to contain the final dilute NaOH above.