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Chem/Phys Final Exam 4 > Spectrometry > Flashcards

Flashcards in Spectrometry Deck (31)
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1

Qualitative Analysis

1. What is the identity or properties of the drug or substance?
2. Separation, isolation, or purification required in most cases, but not all

2

Quantitative Analysis

1. How much substance is present

3

Major identification technique involves the interaction of the molecules of interest with ____________________

Electromagnetic Energy

4

Electromagnetic energy has properties of ________ and has ____________ and wavelengths

1. Properties of waves
2. Has frequency

5

Frequency

1. Hertz (hz) (1 cycle/second), kilohertz (1,000 cycles/sec)
2. Think of it as how quickly it gets to you

6

Wavelengths

1. Meters
2. Think of a typical wave going up and down
Example: standing on beach- every time waves hits you that's the frequency. Distance between the peaks and trophy is the wavelength

7

1 micron (u)

10-6 meters

8

1 nanometer (nm)

10-9 meters (1 mu)
Most frequently seen in chemistry

9

1 angstrom (A)

10-10 meters

10

The Electromagnetic Spectrum: Radio, tv, radar VS x rays and gamma rays?

1. Radio, tv, radar: lower frequency, long wavelengths
2. X rays and gamma rays: high frequency, short wavelengths

11

Wavelengths of the visible part of the spectrum in nanometers and in angstroms:

1. 390 nm-750 nm
2. 4300 A (violet)- 7000 (red)

12

The shorter the wavelength, the ____________ the frequency and the ___________ the energy

1. The greater the frequency
2. Higher the energy

13

Angstrom length (m)

10 (-10)

14

Nanometer Length

10 (-9)

15

Micrometer

10 (-6)

16

Millimeter length

10 (-3)

17

Centimeter length

10 (-2)

18

Meter length

1

19

As molecules are exposed to light (or other energy) they can absorb energy by:

1. Electromagnetic excitation: electrons in the molecule goes from low energy state to a higher energy state
2. Molecular vibrations: each compound has a natural vibration frequency

20

After a molecule is excited it can release the energy in various forms: (3)

1. Heat **** most common result
2. Rupture of molecule
3. Re-emission of energy as altered electromagnetic energy (fluorescence)

21

The useful parts of the spectrum are UV, visible, and ________ radiation?

1. Infrared radiation

22

UV and visible absorption:

1. Electronic absorption (electrons in molecules are excited to a higher energy state). Then they relax and emit energy

23

Infrared absorption is due to:

1. Vibrational energies of a molecule: bending, stretching, and rotation. (lower energy radiation)

24

Most molecules have chromophores that do what?

1. Absorb light.
2. Chromophores may be certain molecular groups, such as phenyl groups or double bonds

25

Basic instrument components: (4)

1. Energy source to produce radiation, usually UV or visible light by deuterium (UV) or tungsten lamp (visible)
2. A system to select limited part of spectrum (prism or grating)
3. Sample chamber
4. Detector (photomultiplier tube-converts light energy to electrical energy)

26

For any compound, absorbency is proportional to: (2)

1. The thickness of the cuvette (or light path)--- thicker=more absorption
2. Concentration of the compound

27

Absorption is dependent on the probability of radiation causing an electron being ___________ in the substance?

1. Electron being excited.
2. If coefficient is small, substance poorly absorbs light

28

Light intensity across a cell is exponential decay equation?

Log 10= IO/I = K X L / 2.303

I= emergent light
IO= incident light
K= constant for any pure compound
L= length of light path

Therefore, absorbance is proportional to the thickness of the cell (L)

29

Absorbance, extinction and optical density?

1. All mean the same thing, that light is being absorbed

30

Beer- Lambert Law

A= E X L X C

If c is measured in moles x L (-1), and length (L) is in cm, then E has the units of L x moles (-1) x cm (-1). This is referred to as the molar absorption coefficient
Note: beer-lambert law assumes one wavelength