Question

Prelaboratory assignment Exp. 4 Beer’s Law

1.Calculate the Concentration of the Crystal Violet Solutions in Table 1 of the Procedureusing Vinitial x Minitial = Vdiluted x Mdiluted (Note: Vdiluted = 15 mL). Record the concentrationsin Table 1 AND in the Data table in the report sheet.

2.Plot the following data as absorbance vs concentration of X in excel

Absorbance, A    Molar Concentration of X
0.045 3.0 x 10-4 mol/L
0.097 6.2 x 10-4 mol/L
0.14 9.0 x 10-4 mol/L
0.35    2.2 x 10-3 mol/L
0.51    3.2 x 10-3 mol/L

When plotting in excel make sure that (in EXCEL, not hand written) you label each axis and place a title that includes your name.

Perform linear regression on the data. Print out and attach to the prelaboratory assignment. If you need help with excel refer back to the excel lab.

Use the graph to answer the following questions.

a.What is equation of the line for this graph and what is its R2 value?

b.What is the Molar concentration of X when its absorbance is 0.23?

c.A 5.0 x 10-3M solution would have an absorbance of?

d.What would be the absorbance if the pathlength in question 3 was doubled?

Prelaboratory assignment Exp. 4 Beer's Law 1. Calculate the Concentration of the Crystal Violet Solutions in Table 1 of the Procedure using Val Mi V ox M ed (Note: Valed15 mL). Record the concentrations in Table 1 AND in the Data table in the report sheet. 2. Plot the following data as absorbance vs concentration of X in excel Absorbance, A Molar Concentration of X 0.045 3.0 x 10 mol/L 0.097 6.2 x 10 mol/L 0.14 9.0 x 10 mol/L 0.35 2.2 x 10 mol/L 0.51 3.2 x 10 mol/L When plotting in excel make sure that (in EXCEL, not hand written) you label each axis and place a title that includes your name. Perform linear regression on the data. Print out and attach to the prelaboratory assignment. If you need help with excel refer back to the excel Lab. Use the graph to answer the following questions. a. What is equation of the line for this graph and what is its R value? b. What is the Molar concentration of X when its absorbance is 0.23? c. A 5.0 x 10M solution would have an absorbance of? d. What would be the absorbance if the pathlength in question 3 was doubled?

skip question number one, it was based off the other section of the assignment which I already completed. thank you so much!

Answer 1

to C O NSILIARIO C D E R8 A B con. of (mol/L) Abs 3.00E-04 0.045 6.20E-04 0.097 9.00E-04 0.14 2.20E-03 0.35 3.20E 03 0.51 Absorbance vs Concentration NIMI 0.6 10.5 Y= 160.4x -0.003 R2 = 1 04 Abs 03 02 10 01 11 12 13 0.00E+00 5.00E-04 1.00E-03 1 50E-03 200E-03 2.50E-03 3.00E-03 350E-03 14 Con of x (mol/L) 15 16 12 18

( Plotting concentration on x axis. & absorbance on y axis we get best fitted lineas equation : y = 168.96- 0.003 ... 6) R² = 1 (a) Fanation for this graph is = 160.4. – 0.003 & pe value in l. e putting a p = 0.23 into sanation (i) we get 0:23 = 160•4 V - 0.003 .: 16044 = 0.23 +0:03 166.= 0.233 ar 0:283 = 145 x40 *° ano! .. when absorbance is 0.23 then molar concentration of x' is ru5x10 -3 mol/ (c) Putting a=50810-3 in to equation (1) - 168.4 x (5.0x103) – 0.003 0799 " A 50 x 10 -3 sowlion would have absorbance of 0.799 anestion (3) is not clear. But according to Beed's law. Abosor barce A) & path length (e) So, if path length is doubled then absorbance also be double