1. A compound has a molar absorptivity of 9300 L/mol-cm at 395 nm. Calculate the molarity of a solution of this compound that has an absorbance of 0.425 when measured in a 1.00 cm cell.

2. The concentration of an unknown solution was found to have a concentration of 5.7 ppm Ca. This solution was made by pipeting 10 mL of a solution, made by dissolving 628 mg of a solid unknown sample in 500 mL, into a 100 mL flask, adding 10 mL of a buffer, and then diluting to the mark. What is the % Ca in the sample?

Give the reason or rational for each of the following facts about UV-vis absorptions.

3. Cr+2 is sky blue in water but Ca+2(aq) is colorless.

4. Acetone absorbs in the UV but not ethanol.

5. Naphthalene absorbs at a longer wavelength than benzene.

6. Which of the following would absorb in the vis-UV region?

a) Ca+2(aq) b) Cr+2(aq) c) Mg+2 d) Pb+2 e) both a and c

7. Which of the following would absorb in the vis-UV region?

a) Na+(g) b) Na(g) c) Ca+2(g) d) Na+(aq) e) none of these

8. Which of the following would absorb in the vis-UV region?

. a) Ethanol b) Acetone c) Ethane d) none of these e) all of a,b,c

9 Which of these would absorb in the IR region?

a) O2 b) N2 c)Ar d) H2O e) all except b

10. A .05 M solution has a %T of 25 when placed in a 1 cm cuvet. What is the molar extinction coefficient of this compound?

 11.  The  monochromator  of  the  Spectronic  20  consists  of  a   ___________ and a ________.    

a) shutter, prism b) prism, occluder

c) diffraction grating, slit   d) prism, slit

e) prism, photocell   

 
12. The detector on the Spectronic 20 consists of a

 
a) Thermister  b) Thermocouple  c) Hollow Cathode Lamp d) Tungsten Lamp e) Phototube