- Determining The K For Bromocresol Green Videos Episode 1 Kcc Fall20 Chem12 Bromocresol Green Indicator Introducti 1 (53.9 KiB) Viewed 67 times
- Determining The K For Bromocresol Green Videos Episode 1 Kcc Fall20 Chem12 Bromocresol Green Indicator Introducti 2 (53.9 KiB) Viewed 67 times
- Determining The K For Bromocresol Green Videos Episode 1 Kcc Fall20 Chem12 Bromocresol Green Indicator Introducti 3 (60.13 KiB) Viewed 67 times
- Determining The K For Bromocresol Green Videos Episode 1 Kcc Fall20 Chem12 Bromocresol Green Indicator Introducti 4 (49.1 KiB) Viewed 67 times
- Determining The K For Bromocresol Green Videos Episode 1 Kcc Fall20 Chem12 Bromocresol Green Indicator Introducti 5 (40.76 KiB) Viewed 67 times
- Determining The K For Bromocresol Green Videos Episode 1 Kcc Fall20 Chem12 Bromocresol Green Indicator Introducti 6 (31.6 KiB) Viewed 67 times
- Determining The K For Bromocresol Green Videos Episode 1 Kcc Fall20 Chem12 Bromocresol Green Indicator Introducti 7 (14.42 KiB) Viewed 67 times
- Determining The K For Bromocresol Green Videos Episode 1 Kcc Fall20 Chem12 Bromocresol Green Indicator Introducti 8 (47.1 KiB) Viewed 67 times
Table 2 Finding the molarity of acetic acid (HC₂H₂O₂) in solution B Molarity of acetic acid solution on bottle 1.00 M Volume of acetic acid solution used in dilution 25.0 mL (mL) Volume of acetic acid solution used in dilution (L) Moles of acetic acid solution (mol) Total volume of solution in dilution (mL) Total volume of solution in dilution (L) Molarity of acetic acid in diluted solution (M) 100.0 mL Volume of acetic acid solution used in dilution (L): Volume of acetic acid solution used in dilution (mL) x 10-³L 1 ml. Moles of acetic acid solution (mol): Molarity of acetic acid solution on bottle=; Total volume of solution in dilution (L): Total volume of solution in dilution (mL) x 10- 1 ml moles of acetic acid in solution (mol) Volume of acetic acid solution used in dilution (L) Molarity of acetic acid in diluted solution (M): moles of acetic acid in solution (mol) Molarity of acetic acid in diluted solution (M)= Total volume of solution in dilution (L) Table 3: Moles of Acetic Acid: Volume of Acetic Acid Solution Added (mL) 2.00 4.00 6.00 8.00 Volume of Acetic Acid Solution Added (L) Molarity of Acetic Acid Solution (M) Volume of Acetic Acid Solution Added (L): Use the following equation for 2.00, 4.00, 6.00, and 8.00 mL Moles of Acetic Acid Added (mol) Volume of Acetic Acid Solution Added (L) = Volume of Acetic Acid Solution Added (mL) x- 10-L 1 mL
Molarity of Acetic Acid Solution (M) No calculation required. This value was already calculated in the last table. Moles of Acetic Acid Added (mol): Molarity of acetic acid in diluted solution (M)= Table 4 Volume of Moles of Moles of Acetic Acetic Sodium Acid Solution Added (mL) 2.00 4.00 6.00 8.00 Acid (mol) pH =pK₂ + log Acetate (mol) moles of acetic acid in solution (mol) volume of acetic acid solution added (L) (mol NaAc mol HAC moles of sodium acetate moles acetic acid Log 'mol NaAc mol HAC moles of sodium acetate moles acetic acid Divide the moles of sodium acetate (column 3) by moles of acetic acid (column 2) (mol NaAc Log mol HAC Take the log of the values from the previous column. pH: pk₂ of HAC Moles of Acetic Acid (mol): These values have already been calculated in the last column of table 3. Transfer those values to this column. Moles of Sodium Acetate (mol): This value will be the same for the entire column. The value has already been calculated in the last row of table 1, under the title, moles of sodium acetate used in dilution (mol). Transfer this value to this column. 4.74 4.74 4.74 4.74 PH
Table 5: All 0.494 0.494 0.494 0.494 Corrected Ax: Corrected Absorbance =Ax 4.00 6.00 8.00 A₁ 0.005 0.005 0.005 0.005 The A, values were determined during part 2 of the lab: Volume of Acetic Acid Solution Added (ml) 2.00 log- A₁-A₁-log A₁-A, Corrected A, Plug in the appropriate Ax value and the volume added in ml Sample: Corrected absorbance when 2.00 mL was added: Corrected absorbance = 0.312( = 100mL+V added 100 mL [HB] Sample: A-A 0.318-0.005 0.313 Au-Ax 0.494-0.318 0.176 A-A A₁-A, (100 ml +2.00 ml) 100 mL = 0.318 A₁-A₁ A₁-A, Absorbance (A.) 0.312 0.227 0.176 0.150 1 For the next to columns plug carefully into the equations using the needed values. A₂-A, A₁-A, 1.778409091 = 1.78 log- -log = [HB] PH
log = log(1.78) = 0.25042002 = 0.250 Ay-A Au-Ax Note: Two of your answers for this part will be negative. pH: These values have already been calculated. The values are in the last column of table four. Transfer the numbers. Graphical Analysis: To find the equilibrium constant (Ka) of bromocresol green we need to perform a plot of log versus [HB-1 pH. Using excel produce a graph using the values from the last two columns of table 5. Title: Determine the Ka for BCG x-axis = pH y-axis = log [HB] Take the linear fit of the line. Copy and paste your graph into your lab report. Using the y intercept of the line you can determine the K, for the bromocresol green. log: [HB] =pH+log K MI = mx + b=logk The calculation for the K, value should be shown on your calculation sheet. The final answer needs to be transferred to your Calculation tables, where it is indicated.
Example of the Graph: 1 яни сар бо 0.2 0.0 -0.2 -0.4 Equilibrium Constant of BCG y Mx B M-0.96021, B-4.7647 Mean Sqr Err-4.12E-05 pH
Post Lab Questions: 1. What are the colors for the acidic form and basic form? 2. For the first part of the lab, the following graph was produced. Absorbance Curves for BCG 0.6 p basic form acidic form Mixed (absorbance) 0.5 0.4 0.3 0.2 0.1 0.950 400 450 500 550 600 wavelength (nm) 650 700 Wavelength of maximum absorbance for base form a. The graph shows that the basic form has a maximum absorption at Amax, while the acidic has its minimum absorption at Amax Explain why the basic form and acidic form have opposite absorptions at this specific wavelength. b. What is the importance of determining the Amax? 3. The accepted K, value for Bromocresol green is 1.6 x 10³. Using your measured value, determine the percent error. % error= |accepted-measured | x 100 accepted 4. When we calculate the pH of the solutions it is found by using the following equation: mol NaAc pH =pK,+ log ( mol HAC Bromocresol green is a weak acid, just like acetic acid. But our calculations assume that bromocresol green does not affect the overall acidity (pH) of the acetate solution. Why is this a good assumption?