Please write the procedure in your own words Please write it in a paragraph Please please please answer as fast as possible please NOTE: Both images go together

Macroscale and Microscale Organic Experiments
7th Edition
ISBN:9781305577190
Author:Kenneth L. Williamson, Katherine M. Masters
Publisher:Kenneth L. Williamson, Katherine M. Masters
Chapter6: Steam Distillation, Vacuum Distillation, And Sublimation
Section: Chapter Questions
Problem 11Q
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Please write the procedure in your own words Please write it in a paragraph Please please please answer as fast as possible please NOTE: Both images go together
PART A - PREPARATION
1. Obtain an unknown sample from your instructor. If the sample is not labeled with the
quantity of sample to use for each run, ask your instructor for the information. Keep the
unknown tightly stoppered to avoid absorption of moisture from the air. Record the
unknown number and the concentration of the standard NaOH (to 4 significant figures).
Weigh the sample on a weighing boat to ±0.0001 g, and transfer the solid directly to a
250 mL beaker. Add approximately 20 mL of water, mixing it well until it is dissolved. If
it does not dissolve, heat the mixture gently on a hotplate (NOT with a Bunsen burner!).
After the sample has dissolved, let it cool slightly and add enough water to bring the
volume up to approximately 100 mL.
NOTE: In this experiment, the amount of the weak acid is determined through weighing.
The volume of water does not appear in the calculation and therefore it is not important to
measure it precisely.
2. You will need approximately 50 mL of standardized NaOH solution for each titration.
The concentration should be about 0.1 M. Clean, condition, and fill a buret with the
standard NaOH solution. Your initial reading should be 0.00 mL.
3. Connect a pH sensor to Channel 1 of the Vernier handheld unit. Connect the handheld
unit to the computer using the USB cable. Calibrate the pH sensor as you did in the
previous experiment, using the 4.0 and 7.0 buffers.
PART B - TITRATION
1. Place the beaker with the unknown sample on a stirring plate and put in a stirring bar.
Rinse and dry the sensor with a Kimwipe, and insert it into the unknown weak acid
solution so that the tip is at least 0.5 inch to 1 inch below the surface and away from the
magnetic stirring bar. (The glass bulb must be covered by solution.) The stirrer should be
turned off before any pH readings are taken.
electrode
Figure 2. The
titration set-up.
Stirring bar
Magnetic stirrer
2. Run the Logger Pro program on your computer. Open the file "07a Acid-Base" from the
Advanced Chemistry with Vernier folder.
3. You are now ready to begin the titration.
a. Before adding any NaOH titrant, click Collect. Once the displayed pH reading has
stabilized, click > Keep. In the edit box, type 0.00 (for 0 mL base added). Press the
ENTER key to store the first data pair for this experiment.
b. Add the next increment of NaOH (enough to raise the pH by about 0.15 units). When
the pH stabilizes, again click Keep. In the edit box, type the buret reading and press
ENTER. This is the second data pair for the experiment.
Transcribed Image Text:PART A - PREPARATION 1. Obtain an unknown sample from your instructor. If the sample is not labeled with the quantity of sample to use for each run, ask your instructor for the information. Keep the unknown tightly stoppered to avoid absorption of moisture from the air. Record the unknown number and the concentration of the standard NaOH (to 4 significant figures). Weigh the sample on a weighing boat to ±0.0001 g, and transfer the solid directly to a 250 mL beaker. Add approximately 20 mL of water, mixing it well until it is dissolved. If it does not dissolve, heat the mixture gently on a hotplate (NOT with a Bunsen burner!). After the sample has dissolved, let it cool slightly and add enough water to bring the volume up to approximately 100 mL. NOTE: In this experiment, the amount of the weak acid is determined through weighing. The volume of water does not appear in the calculation and therefore it is not important to measure it precisely. 2. You will need approximately 50 mL of standardized NaOH solution for each titration. The concentration should be about 0.1 M. Clean, condition, and fill a buret with the standard NaOH solution. Your initial reading should be 0.00 mL. 3. Connect a pH sensor to Channel 1 of the Vernier handheld unit. Connect the handheld unit to the computer using the USB cable. Calibrate the pH sensor as you did in the previous experiment, using the 4.0 and 7.0 buffers. PART B - TITRATION 1. Place the beaker with the unknown sample on a stirring plate and put in a stirring bar. Rinse and dry the sensor with a Kimwipe, and insert it into the unknown weak acid solution so that the tip is at least 0.5 inch to 1 inch below the surface and away from the magnetic stirring bar. (The glass bulb must be covered by solution.) The stirrer should be turned off before any pH readings are taken. electrode Figure 2. The titration set-up. Stirring bar Magnetic stirrer 2. Run the Logger Pro program on your computer. Open the file "07a Acid-Base" from the Advanced Chemistry with Vernier folder. 3. You are now ready to begin the titration. a. Before adding any NaOH titrant, click Collect. Once the displayed pH reading has stabilized, click > Keep. In the edit box, type 0.00 (for 0 mL base added). Press the ENTER key to store the first data pair for this experiment. b. Add the next increment of NaOH (enough to raise the pH by about 0.15 units). When the pH stabilizes, again click Keep. In the edit box, type the buret reading and press ENTER. This is the second data pair for the experiment.
C.
Continue adding NaOH in increments that raise the pH by about 0.15 units and enter
the buret reading after each increment. When a pH reading of 4-4.5 is reached, switch
to smaller increments. You will want to be adding one or two drops at a time as you
approach the equivalence point.
d. After a pH reading of approximately 10 is reached, add larger increments that raise
the pH by about 0.15 pH units and enter the buret reading after each increment. You
may stop adding base and taking readings about four milliliters after the titration
curve begins to level off.
4. When you have finished collecting data, click STOP. Dispose of the reaction mixture
as directed. Rinse the pH sensor with deionized water in preparation for the second
titration.
5. Follow the steps below to find the equivalence point, which will be where there is the
largest increase in pH upon the addition of a very small amount of NaOH solution. A
good method of determining the precise equivalence point of the titration is to take the
second derivative of the pH-volume data, a plot of A²pH/Avol².
a. View a plot of the second derivative on Page 3 by clicking on the Next Page button.
b. Analyze the second-derivative plot and determine the volume of NaOH at the
equivalence point. The equivalence point is the x-intercept; the second derivative (f")
will go from a high positive value to a big negative value. Use the range markers and
the linear regression function to get an equation for the line connecting the high and
low f' values, and then solve for x. That will be Vep.
6. The buffer-point volume (Vbp) will be one-half the equivalence-point volume. Using the
titration-curve graph, put the range markers around Vы and a couple data points on each
side. (This part of the graph should be essentially linear.) Use the range markers and the
linear regression function to get an equation for the line, and then solve for y. This will be
the pH at the buffer point; it is also the pKa.
7. Print your graphs and the appropriate data. For the pH titration graph, the data showing
should be in the buffer region. For the second-derivative graph, the data showing should
be around the equivalence point. If you wish to save your results, choose Store Latest
Run from the Experiment menu.
8. Perform a second titration. If your added increments were too large in your first run,
make the necessary modifications to your procedure.
9. Perform a third titration if necessary.
Transcribed Image Text:C. Continue adding NaOH in increments that raise the pH by about 0.15 units and enter the buret reading after each increment. When a pH reading of 4-4.5 is reached, switch to smaller increments. You will want to be adding one or two drops at a time as you approach the equivalence point. d. After a pH reading of approximately 10 is reached, add larger increments that raise the pH by about 0.15 pH units and enter the buret reading after each increment. You may stop adding base and taking readings about four milliliters after the titration curve begins to level off. 4. When you have finished collecting data, click STOP. Dispose of the reaction mixture as directed. Rinse the pH sensor with deionized water in preparation for the second titration. 5. Follow the steps below to find the equivalence point, which will be where there is the largest increase in pH upon the addition of a very small amount of NaOH solution. A good method of determining the precise equivalence point of the titration is to take the second derivative of the pH-volume data, a plot of A²pH/Avol². a. View a plot of the second derivative on Page 3 by clicking on the Next Page button. b. Analyze the second-derivative plot and determine the volume of NaOH at the equivalence point. The equivalence point is the x-intercept; the second derivative (f") will go from a high positive value to a big negative value. Use the range markers and the linear regression function to get an equation for the line connecting the high and low f' values, and then solve for x. That will be Vep. 6. The buffer-point volume (Vbp) will be one-half the equivalence-point volume. Using the titration-curve graph, put the range markers around Vы and a couple data points on each side. (This part of the graph should be essentially linear.) Use the range markers and the linear regression function to get an equation for the line, and then solve for y. This will be the pH at the buffer point; it is also the pKa. 7. Print your graphs and the appropriate data. For the pH titration graph, the data showing should be in the buffer region. For the second-derivative graph, the data showing should be around the equivalence point. If you wish to save your results, choose Store Latest Run from the Experiment menu. 8. Perform a second titration. If your added increments were too large in your first run, make the necessary modifications to your procedure. 9. Perform a third titration if necessary.
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