Quiz 1

Question 1

Light is…

Answer 1

Reflected, transmitted, absorbed

Question 2

What is transmittance (T)?

State the formula

Answer 2

• The fraction of light that passes through the sample
• T = I/I0
  
  • I0 = radiant power of incident light
  • I = radiant power of light that passes through sample

Question 3

What does a spectrometer measure?

Why do we set the sepctrometer blank to 100% transmittance?

Answer 3

• Light transmitted
• To compensate for absorbance by the solvent, and for the reflection of light off the tube (3 mL)

Question 4

What is absorbance (A)?

State lambert’s law

State the formula

Answer 4

• Amount of light absorbed
  
  • Lambert’s Law: for a thin layer of sample, the same proportion of light is absorbed regardless of I₀
    
    • Each layer absorbs 1/2, then 1/2 of that, then 1/2 of that, and so on
• A = log(1/T) = log(I₀/I)

Question 5

State beer’s law

Answer 5

Beer’s Law: the absorbance of a solution is proportional to the number of absorbing particles

• A = E x l x c
  
  • E = absorption coefficient (M-1/cm)
    
    • Measures probability that photon will be absorbed; varies with wavelength and solvent used
  • c = concentration of solution (M)
  • l = path length through the spectro tube (usually 1 cm)

Question 6

State the prefixes in units of measure and how to get to them from the OG unit

• Kilo
• Centi
• Milli
• Micro
• Nano

Answer 6

• Kilo = standard unit (ex., metres) / 1000
• Centi = standard unit x 100
• Milli = standard unit x 1000
• Micro = standard unit x 10⁶
• Nano = standard unit x 10⁹