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Analytical Chemistry > Instrumental Methods of Analysis ❗️ > Flashcards

Instrumental Methods of Analysis ❗️ Flashcards

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1
Q

What are the three instrumental methods of analysis?

A
  • spectroscopy
  • electrochemistry
  • chromatography
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2
Q

What is analytical chemistry divided into?

A

1) Chemical methods
2) Physical methods

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3
Q

What are the different chemical methods?

A

1) gravimetric method
2) volumetric method

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4
Q

What are instrumental methods about?

A

determining chemical compositions of compounds

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5
Q

What is classical analysis?

A

signal depends on the chemical properties of the sample:
- a reagent reacts completely with the analyte
- the relationship is measured between the analyte and titrant

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6
Q

What is instrumental analysis?

A

a physical property of the sample is measured:
- electrical potential
- pH
- etc.

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7
Q

What are the types of instrumental (physical) methods?

A

1) optical methods
2) chromatographic methodds
3) electrochemical methods

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8
Q

Why are the advantages of instrumental methods?

A

1) speed
2) sensitivity
3) selectivity (accurate in presence of many different components)
4) reproducibility
5) small sample requirements

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9
Q

Why are the disadvantages of instrumental methods?

A

1) cost
2) complexity
3) maintenance (eg. breaking of lab equipment, clogging of equipment, etc.)

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10
Q

What is an analytical technique?

A

Scientific phenomenon giving information on the composition of substances.

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11
Q

What is an analytical method?

A

specific application of technique used to solve an analytical problem.

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12
Q

What is a procedure?

A

instructions formilated to carry out a method (lists out steps to be followed for analysis).

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13
Q

What is a protocol?

A

The most specific description of a method.
- detailed directions must be followed without exception

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14
Q

What is a basic block diagram for instrumental measurements?

A

stimulus (energy) –> system under study –> response (analytical information)

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15
Q

What is absorption?

A

Process by which the energy of light (in the form of photons) is transferred to the atom or molecule raising them from the ground state to the excited state.

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16
Q

When does emission/radiation happen?

A

When molecules/atoms fall back down to lower energy levels, emitting radiation.

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17
Q

What is fluorescence?

A

absorbed energy is rapidly lost to the surroundings by collisions within the system and relax back to the ground state.

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18
Q

What is Beer-Lambert-Bouguer law?

A

relates the attentuation of light to the properties of the material through which the light is passing.

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19
Q

What is the equation of Beer-Lambert-Bouguer law?

A

A=Elc
A- absorbance
E- energy
l- optical path length
c- concetration of chemical species in mol/L

absorbance = path length
absorbance = sample concentration
= direc. prop

20
Q

What is electromagnetic radiation?

A

form of energy that is transmitted through space at enourmous velocities.
electric field, magentic field, and electromagnetic wave are all at 90 * angles

21
Q

What is wavelength?

A

distance from crest units (maximum points/minimum points)

22
Q

What is frequency?

A

number of waves per second (Hz, Hertz)

23
Q

What is wave number?

A

the number of waves per unit length

24
Q

What is power? What else is it called?

A
  • energy per unit time,
  • also known as intensity
25
Q

What is paramagnetic spectroscopy?

A

microwave technique based on the splitting electronic fields in a magnetic field.
- used to determine structures of samples containing unpaired electrons

26
Q

What is a different name for “infrared spectroscopy”?

A

“molecular fingerprint”
- used to identify materials,
- quantify the number of absorbing molecules

27
Q

What is x-ray spectroscopy?

A
  • excitation of inner electrons of atoms, which may be seen as x-ray absorption.
  • an x-ray fluorescence emission spectrum may be used
28
Q

What is electrochemistry?

A
  • concered with the interelation of electrical and chemical effects

eg. measurement of electrical quantities, current, potential, their relationship and parameters.

29
Q

What is an electric current?

A

flow of charge through a medium
- moving electrons in a conductor
- carrid by ions in electrolyte
- carried by electrons and ions in plasma

30
Q

What is potential?

A
  • quantitative description of the driving force behind an electrochemical reaction
31
Q

What is an electrochemical cell?

A

A cell consisting of two electronic conductors (electrodes) dipped into a solution (containing ions and electrolytes).

32
Q

How does a pH sensor work?

A

based on an electric potential difference (build up of h+ ions within the pH meter)

33
Q

What is potentiomentry?

A

measurement of electric potential

34
Q

What are the two types of indicator electrodes?

A

1) metal electrodes (develop an electric potential in response to a redox reaction at the metal surface).
2) ion selective electrode (bind one type of ion to a membrane to generate an electric potential).

35
Q

How is electric potential generated?

A

by the build up of H+ ions on one side of the glass meter.

36
Q

What are the advantages of pH meters?

A

1) potentail is not affected by its presence of oxidizing or reducing agents
2) wide pH range
3) responds fast and functions well in physiological systems

37
Q

What is chromatography?

A

technique for seperating mixtures into their components by their distinctive mechanisms of interations (reactions) of the solute (mobile phase) with the stationary phase. Differences occur due to differences in:
- size
- charge
- shape

38
Q

What type of gel is used?

A

silica gel

39
Q

What are the two phases in chromatography?

A

1) stationary phase (solvent)
2) mobile phase (column packing material)

40
Q

What is chromatography used for?

A
  • analyzing
  • identifing
  • purifing
  • quantifing
41
Q

What are the two types of chromatography?

A

1) column
2) planar

42
Q

What is column chromatography?

A
  • glass tube filled with silica gel
  • fresh solvent is set on top

solvents seperate due to their mobile phases.

43
Q

What is planar chromatography?

A
  • stationary phase is placed on a flat plate and the mobile phase travels across it by gravity or capillary.
  • paper chromatography
44
Q

What is dissociation?

A

a substance dividing into ions and cations

45
Q

What are strong electrolytes

A

Analytical Chemistry (12 decks)

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