4. A1.00 L buffer is made containing 50.0 mmol of bromoacetic acid (pKa 290 and

Question

4. A1.00 L buffer is made containing 50.0 mmol of bromoacetic acid (pKa 290 and 75.0 mmol of sodium bromoacetate. What volume of 2.00 M NaOH must be added to increase the pH ofthis buffer to 4.00? 5. How does a photomultiplier tube detect fluorescence from a sample? 6. X and Y are two compounds that absorb infrared radiation. The transmittance ofo.0100Mx and 0,0100 MY were obtained in a 0.00500 cm cell and are listed on the following page (measured at the wavenumber of maximum ab mum transmittance for each compound, respectively). A mixture of A and B in a 0.00500 cm cell had a transmittance of 34.0% at 2022 cm 1 and 38.3 at 1993 cm 1. What are the concentrations ofx and Y in the mixture? Wavenumber (cm Pure A Pure B 31.0 T 97.4 T 2022 79.7% T 20.0% T 1993 7 The calcium content of a person's urine was determined on two different days. Are the average values significantly different at the 95% level? Number of [Cal (mg/L) measurements Day 235 at 9 251 8

Explanation / Answer

Solution:

We know from Beer-Lambert’s law:

A=Cl ------------> (1);

Or, 1/T = Cl -----------> (2)

Or, = 1/TxCl

A= Absorbance, =molar absorption coefficient, C= concentration, l = length of the cell and T = transmittance

Applying equation (2) for compound-X (maximum absorption at max of 2022 cm-1) we have:

1/T = xCxl

Or, 1/31% = xCxl

Or, 100/31 = x x 0.01 x 0.005

Or, x = 100/31x0.01x0.005 = 64516

Similarly, applying equation (2) for compound-Y (maximum absorption at max of 1993 cm-1) we have:

1/T = yCyl

Or, 1/20% = yCyl

Or, 100/20 = y x 0.01 x 0.005

Or, y = 100/20x0.01x0.005 = 100000

Therefore, concentration of X at transmittance of 34% at 2022 cm-1 can be evaluated as follows:

1/T = xCxl

Or, 1/34% = 64516 x Cx x 0.005

Or, 100/34 = Cx x 322.58

Or, Cx = 100/34x322.58 = 0.0091 M

Similarly, concentration of Y at transmittance of 38.3% at 1993 cm-1 can be evaluated as:

1/T = yCyl

Or, 1/38.3% = 100000 x Cy x 0.005

Or, 100/38.3 = Cy x 500

Or, Cy = 100/38.3x500 = 0.0052 M

Related Questions

Navigate

• Browse (All)
• Browse 4
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.