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student name  Work date: Report submission date:  ___________________________  
Student Identification  Experience number and title  Experiment613:Spectrophotometric determination of aspirin 
Experiment613 Spectrophotometric determination of aspirin
Section1: Purpose and summary
It is said that most aspirin tablets contain 5 grains of the active ingredient acetylsalicylic acid. (A grain is a unit of mass and equals 0.0647989 grams.) How reliable is this value? This experience allows you to verify the manufacturer.
The analysis method we use is called "spectrometry" or "spectrophotometry". It depends on molecules being able to absorb electromagnetic radiation of certain wavelengths using the energy of the radiation to 'excite' the electrons in their atoms. (Therefore, they have absorption spectra, just like isolated gas atoms.) The higher the concentration of a given molecule in a sample, the more light of a given wavelength the sample can absorb. The absorption of light by
The sample increases in direct proportion to the concentration of the molecule present. We use electromagnetic radiation ("light") of wavelength (λ) 297 nm, which falls in the ultraviolet range. In this experiment, a 297 nm light is shined through the sample and the amount of light absorbed by the sample is measured.
The chemical name of the active ingredient in aspirin is acetylsalicylic acid. To completely dissolve aspirin in water, you must chemically convert it to the sodium salicylate salt before measuring absorbance. Note that 1.00 mol of sodium salicylate is produced for every 1.00 mol
Uses of acetylsalicylic acid (aspirin):
Sodium salicylate is then reacted with acidic Fe^{3}^{+}to form iron(III) salicylate complex, [FeSal]^{+}. This complex shows maximum absorption at a wavelength of 525 nm and is purple in color. Absorption of [FeSal]^{+}The complex is directly proportional to the concentration of salicylate in the sample but does not tell us the actual concentration in any sample. To convert an instrument reading to an actual salicylate concentration, we must first calibrate the instrument with solutions of known sodium salicylate concentration.
In general, this pilot project consists of:

By carefully preparing 5 solutions ofacquaintanceconcentrations

Measure the absorbance of eachacquaintancemiA strangerSolution

Carefully prepare an aspirin solution (fromA strangerConcentration)

(Depending on the laboratory) Creation of a calibration curve from the data of the 5 solutions ofacquaintanceconcentrations

(After the lab) Using the calibration curve to calculate the amount of aspirin in a tablet or pill.
Section 2: Safety Precautions and Disposal
Safety precautions:
All the materials in this experiment are relatively harmless. Laboratoryderived aspirin should not be consumed. Caustic soda is corrosive. The use of eye protection is recommended for all experimental procedures.
garbage deposit:
Discard solutions down sink drain with plenty of water. Dispose of any filter paper and undissolved residue from the aspirin tablet in the trash.
Section 3: Procedures
Part 1:Prepare solutions of known concentrations.
 Concentration (molarity) of sodium salicylate standard solution: 
 
 
 
 Initial burette value (ml): (Include 2 decimal places!) 
 Burette #1 reading (ml): (Include 2 decimal places!) 
You will then use this volume to calculate the concentration (molarity) of sodium salicylate in solution #1. Let's call this volume "Transfer Volume #1"  Calculate the difference between the initial value of the burette and the value of burette #1. (Include 2 decimal places!) “Transfer Belt #1”: ______________ml 
 
 Buret #2 reading (mL): (Include 2 decimal places!) 
RecordTransfer volume #2. Carefully fill the volumetric flask with 0.010 M FeCl._{3}add exactly to the 100 mL mark in 0.1 M HCl solution and mix well. That's allSolution#2. Empty the 100 mL volumetric flask into the beaker marked "2". Rinse the volumetric flask with plenty of laboratory water.  Calculate the difference between the #1 and #2 buret readings. (Include 2 decimal places!) “Drive Belt #2”: ______________ml 
 Burette #3 Reading (mL): (Include 2 decimal places!) 
RecordTransfer Volume #3. Carefully fill the volumetric flask with 0.010 M FeCl._{3}add exactly to the 100 mL mark in 0.1 M HCl solution and mix well. That's allSolution#3. Empty the 100 mL volumetric flask into the beaker marked "3". Rinse the volumetric flask with plenty of laboratory water.  Calculate the difference between the #2 and #3 buret readings. (Include 2 decimal places!) „Transfer belt no. 3": ______________ml 
 Initial buret value after RELOAD (mL): (Include 2 decimal places!) 
 Reading burette #4 (ml): (Include 2 decimal places!) 
RecordTransfer tape #4. Carefully fill the volumetric flask with 0.010 M FeCl._{3}add exactly to the 100 mL mark in 0.1 M HCl solution and mix well. That's allSolution#4. Empty the 100 mL volumetric flask into the beaker marked “4”. Rinse the volumetric flask with plenty of laboratory water.  Calculate the difference between the #4 burette reading and the initial burette reading after FILL. (Include 2 decimal places!) „Transfer belt no. 4": ______________ml 
 Burette reading #5 (mL): (Include 2 decimal places!) 
RecordTransfer Volume #5. Carefully fill the volumetric flask with 0.010 M FeCl._{3}add exactly to the 100 mL mark in 0.1 M HCl solution and mix well. That's allSolution#5. Empty the 100 mL volumetric flask into the beaker marked “5”. Rinse the volumetric flask with plenty of laboratory water.  Calculate the difference between the #4 and #5 buret readings. (Include 2 decimal places!) "Transfer Tape #5": ______________ml 

paper2:Using an aspirin tablet to prepare a solution of unknown concentration
Read the label on the aspirin bottle to find out how many grains are in each pill. If grains are not reported, record the number of grams.  On the aspirin bottle, indicate the number of GRAINS (if you do not have them, indicate grams) that each tablet should contain: 
 
 
 
 
 
 

paper3:Measurement of ultraviolet light absorption by sodium salicylate solutions
1. See Appendix: Technique I Use of Spec 20/Spec 200 for proper use and operation of the spectrophotometer. 
2. Set up the spectrophotometer to measure absorbance at 525 nm. 
3. Use 0.010 M FeCl_{3}in 0.1 M HCl solution as the reference liquid, ie, set the instrument to zero absorbance when the light path passes through this ferric iron(III) solution. 
Rinse the cuvette (sample holder) well with laboratory grade water and then with each solution between measurements. Enter your data in the following table. 
Investigation  absorption in525New Mexico 
Solution #1  
Solution #2  
Solution #3  
Solution #4  
Solution #5  
A stranger 
Quick check:

The absorbance should increase from solution #1 (lowest) to solution #5 (highest).

The absorbance of the unknown should be between the absorbance of solution #1 and solution #5.
Section 4:calculations
(ºto becan be completed after the internship. However, if time is available, it is recommended that you work on these calculations before you leave the lab, because if an error is found in your data, you may have time to get better data in the lab.)

Calculate the concentration of your known solutions using the dilution equation: M_{1}v_{1}= METRO_{2}v_{2}.
solution name  METRO_{1}= concentration of the solution to be transferred (the initial solution)  v_{1}= Volume transferred  METRO_{2}= final concentration (Calculate this numberwith correct SIGNIFICANT NUMBERS)  v_{2}= final volume of solution after dilutionEsfinished 
fallback solution  Concentration (molarity) of sodium salicylate standard solution (on the standard vial label)=  5,00ml  100,0ml  
solution not  Concentration of your stock solution =  Transfer volume Nr. 1 =  100,0ml  
solution not  Concentration of your stock solution =  Transfer volume Nr. 2 =  100,0ml  
solution not  Concentration of your stock solution =  Transfer volume Nr. 3 =  100,0ml  
solution not  Concentration of your stock solution =  Transmission Band #4 =  100,0ml  
solution not  Concentration of your stock solution =  Transmission Band #5 =  100,0ml 
2. Create the calibration curve
Using Microsoft Excel or another spreadsheet program, plot the final concentration (y values) against the absorbance (x values) for solutions 15. Use Microsoft Excel to find the line of best fit (also known as linear regression).
Basic instructions for creating charts with Microsoft Excel^{®}

Enter the data into the worksheet with the xcoordinate data in the first column and the ycoordinate data in the second column.

Select data columns with the mouse.

Choose Chart Wizard on the toolbar or from the Insert menu.

Select the type of chart you want. Typically xy scatterplot.

choosenextGusto.

If necessary, select the data range (normally not required).

choosenextGusto.

Enter chart titles and data labels.

choosenextGusto.

Choose Insert Chart Asnew page.

Select data points with the mouse.

Add trend line from chart menu or right click.

Choose the type of trend line (linear).

Use the Options tab to include linear equations and r^{2}not graphic value.

Make the chart pretty using the format plot area.

Double click on the axes to adjust the limits.
Write the equation of the line obtained from linear regression(step 14 above):
______________________________________________________________________
Ask your instructor for a graph of your datahe mustto be thereRlaboratory report.

Using the equation written above, calculate the concentration of the unknown solution:
Investigation  absorption in525New Mexico  concentration 
A stranger 
4. From the concentration of the unknown solution, calculate the amount of aspirin in the tablet.
 Concentration of unknown solution: 
METRO_{1}= (calculate) v_{1}= 2,00ml METRO_{2}= concentration of the unknown solution (from the top) v_{2}= 100,0ml  Concentration of unknown solution before dilution: 
Calculate the number of moles of sodium salicylate in the 250.0 mL volumetric flask by multiplying 0.2500 L by the concentration of the unknown solution before dilution.  Mole sodium salicylate: 
 Mol Aspirin: 
 Aspirina Gramm: 
 Aspirin grains: 
(Your aspirin grains  aspirin grains from the bottle) * 100 Cereal aspirin bottle  Error rate: 
PAGostLab Questions:

Discuss your test results: Do your results agree with the aspirin manufacturer's claim regarding grains (or grams) of aspirin in each pill? Discuss any of your experimental errors that might affect your conclusions.

Discuss how the structure of aspirin becomes more soluble in water after reacting with sodium hydroxide.

In another experiment, known ibuprofen solutions were used to create a calibration curve. The best line of fit for this calibration curve was
y=0,000924x+ 0,0000343
where x = absorbance and y = concentration (molarity) of ibuprofen in solution.

If absorbance = 0.207, what is the concentration of ibuprofen in the solution?

Predict absorbance for 5.62 x 10^{4}ibuprofen solution M.

Assume that the anibuprofen tablet is crushed, dissolved in sodium hydroxide, and filtered. This solution is diluted to a total volume of 5.00 L and mixed well. If this solution has an absorbance of 0.163, how many milligrams of ibuprofen were in the tablet? The molar mass of ibuprofen is 206.29 g/mol.