Analytical Chemistry Exam 4

Front 1

What is the most widely used analytical technique

Back 1

Chromatography

Front 2

Chromatography definition

Back 2

a physical method of separation in which components to be separated are distributed between two phases

Front 3

Solutes which interact ___________ ____________ with the stationary phase take longer to pass through the column

Back 3

more strongly

Front 4

Solutes which only ___________ interact with the stationary phase

Back 4

weakly

Front 5

Adsorption chromatography

Back 5

solute adsorbed on surface of stationary phase

Front 6

Ion-exchange chromatography

Back 6

- Mobile anions held near cations are covalently attached to stationary phase
- Small molecules penetrate pores of particles
- anion-exchange resin; only anions can be attracted to it

Front 7

molecular exclusion chromatography

Back 7

- large molecules are excluded
- small molecules penetrate pores of particles

Front 8

Partition Chromatography

Back 8

- Cross section of open tubular column
- solute dissolved in liquid phase bonded to the surface of column

Front 9

Affinity chromatography

Back 9

- One kind of molecule in complex mixture becomes attached to molecule that is covalently bound to stationary phase
- all other molecules simply wash through

Front 10

Longitudinal diffusion

Back 10

band slowly broadens as molecules diffuse from high concentration in band to regions of lower concentration

Front 11

what are the 5 commonly used GC Carrier gases

Back 11

1. helium 2. hydrogen 3. nitrogen 4. argon 5. CO2

Front 12

What is the most common detector for GC

Back 12

Flame ionization detector

Front 13

HPLC Normal Phase

Back 13

- hihgly polar stationary phase
- nonpolar solvent (mobile phase)

Front 14

HPLC reversed-pase

Back 14

- nonpolar stationary phase
- polar mobile phase

Front 15

what is the advantage of EOF

Back 15

NO eddy diffusion and mass transfer term

Front 16

Gravimetric analysis

Back 16

the mass of a product is used to calculate the orginal quantity of the target analyte in the sample

Front 17

percipitant

Back 17

a chemical reagent that causes precipitation of an analyte from a solution

Front 18

In gravimetric analysis, the precipitate should me

Back 18

1. pure
2. insoluble
3. Easily filterable
4. of known composition

Front 19

What are the two phases of crystallization

Back 19

Nucleation and particle growth

Front 20

Nucleation

Back 20

where molecules in solution randomly form small aggregates of molecules

Front 21

Particle growth

Back 21

the addition of more molecules to the aggregate to form a crystal

Front 22

if nucleation >> particle growth

Back 22

many small aggregates

Front 23

If nucleation << particle growth

Back 23

large crystals

Front 24

Why is bad for nucleation to be faster than particle growth

Back 24

you wind up with many small particles in solution and few large ones

Front 25

Ways to improve crystal growth

Back 25

- raise the temperature
- add precipitant slowly
- keep volume of solution large
- control solubility through chemical means

Front 26

homogeneous precipitation

Back 26

the precipitant is generated slowly by a chemical reaction

Front 27

Digestion

Back 27

promotes slow crystallization,
increases particle size,
expulsion of impurities from the crystal

Front 28

Ignition

Back 28

used to drive off water or give an oxide form

Front 29

thermogravimetry

Back 29

is a form of gravimetric analysis where mass is measured as a function of temperature

Front 30

Combustion analysis

Back 30

- used to determine elemental content of organic compounds burned in excess O2
- mass of CO2 and H2O is weighed