Instrumental Methods of Analysis ❗️

Question 1

What are the three instrumental methods of analysis?

Answer 1

• spectroscopy
• electrochemistry
• chromatography

Question 2

What is analytical chemistry divided into?

Answer 2

1) Chemical methods
2) Physical methods

Question 3

What are the different chemical methods?

Answer 3

1) gravimetric method
2) volumetric method

Question 4

What are instrumental methods about?

Answer 4

determining chemical compositions of compounds

Question 5

What is classical analysis?

Answer 5

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

Question 6

What is instrumental analysis?

Answer 6

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

Question 7

What are the types of instrumental (physical) methods?

Answer 7

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

Question 8

Why are the advantages of instrumental methods?

Answer 8

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

Question 9

Why are the disadvantages of instrumental methods?

Answer 9

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

Question 10

What is an analytical technique?

Answer 10

Scientific phenomenon giving information on the composition of substances.

Question 11

What is an analytical method?

Answer 11

specific application of technique used to solve an analytical problem.

Question 12

What is a procedure?

Answer 12

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

Question 13

What is a protocol?

Answer 13

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

Question 14

What is a basic block diagram for instrumental measurements?

Answer 14

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

Question 15

What is absorption?

Answer 15

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.

Question 16

When does emission/radiation happen?

Answer 16

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

Question 17

What is fluorescence?

Answer 17

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

Question 18

What is Beer-Lambert-Bouguer law?

Answer 18

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

Question 19

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

Answer 19

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

Question 20

What is electromagnetic radiation?

Answer 20

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

Question 21

What is wavelength?

Answer 21

distance from crest units (maximum points/minimum points)

Question 22

What is frequency?

Answer 22

number of waves per second (Hz, Hertz)

Question 23

What is wave number?

Answer 23

the number of waves per unit length

Question 24

What is power? What else is it called?

Answer 24

• energy per unit time,
• also known as intensity

Question 25

What is paramagnetic spectroscopy?

Answer 25

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

Question 26

What is a different name for "infrared spectroscopy"?

Answer 26

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

Question 27

What is x-ray spectroscopy?

Answer 27

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

Question 28

What is electrochemistry?

Answer 28

- concered with the interelation of electrical and chemical effects eg. measurement of electrical quantities, current, potential, their relationship and parameters.

Question 29

What is an electric current?

Answer 29

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

Question 30

What is potential?

Answer 30

- quantitative description of the driving force behind an electrochemical reaction

Question 31

What is an electrochemical cell?

Answer 31

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

Question 32

How does a pH sensor work?

Answer 32

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

Question 33

What is potentiomentry?

Answer 33

measurement of electric potential

Question 34

What are the two types of indicator electrodes?

Answer 34

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).

Question 35

How is electric potential generated?

Answer 35

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

Question 36

What are the advantages of pH meters?

Answer 36

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

Question 37

What is chromatography?

Answer 37

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

Question 38

What type of gel is used?

Answer 38

silica gel

Question 39

What are the two phases in chromatography?

Answer 39

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

Question 40

What is chromatography used for?

Answer 40

- analyzing - identifing - purifing - quantifing

Question 41

What are the two types of chromatography?

Answer 41

1) column 2) planar

Question 42

What is column chromatography?

Answer 42

- glass tube filled with silica gel - fresh solvent is set on top solvents seperate due to their mobile phases.

Question 43

What is planar chromatography?

Answer 43

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

Question 44

What is dissociation?

Answer 44

a substance dividing into ions and cations

Question 45

What are strong electrolytes