Lab Midterm

Question 1

Chromatography

Answer 1

a versatile physical method of separation and characterization by which two or more components in a mixture are distributed

Question 2

TLC-

Answer 2

Thin Layer Chromatography

• involves spotting the sample being analyzed near the bottom of the TLC plate
• based upon the relative attraction between the surface of solid stationary phase and the components o the mixture versus those between the liquid solvent (mobile phase) and components of the mixture

Question 3

Absorption

Answer 3

The attachment of molecules to the surface of a solid, implies penetration of molecules into the solid

Question 4

How it works… TLC

Answer 4

after placed in the shallow layer of suitable solvent… components absorbed on the stationary phase and dissolves in the mobile phase to a different extent. Components less strongly absorbed onto the stationary phase and more soluble in the mobile phase travel up the plate farther than other components.

Question 5

Know how we were able to see the separation of the analgesics even though they are all colorless

Answer 5

using UV lighting a fluorescent dye which glows green indicates which substances traveled when exposed to UV light.

Question 6

Components in Chromatography travel farther

Answer 6

based on their polarity. Each component interacts with (absorbs on) the stationary phase and dissolves in the mobile phase. Components less strongly absorbed onto the stationary phase and more soluble in the mobile phase travel up the plate farther than other components.

Question 7

Retention Factor

Rf= d ingred./ d solvent

Answer 7

The distance traveled by each component is expressed as a rate or retention factor. Rf values of analgesic ingred. separated by TLC are calculated by dividing the distances traveled by an ingred. by the distance traveled by the solvent measured from the origin point where the spot was initially applied to the place

Question 8

Chromatography is used to i.d. substances by

Answer 8

comparing them to like compounds because they will travel in similar fashion.

Question 9

Filter Paper

Answer 9

helps keep the atmosphere within the chamber saturated w/ the solvent vapor at all times

Question 10

Watch Glass

Answer 10

keeps the solvent from evaporating from the chamber

Question 11

Spots are small b/c

Answer 11

so they do not tail and overlap with eachother

Question 12

Volatile

Answer 12

ability to evaporate

Question 13

Filtrate

Answer 13

to separate a solid from a fluid

Question 14

Solubiltiy

Answer 14

a solutes ability to dissolve in a solid liquid or gaseous solvent to form a solution

Question 15

Matter

Answer 15

anything with mass that takes up space

Question 16

Substance

Answer 16

fixed composition and properties

Question 17

Element

Answer 17

atoms of all the same type

i.e. carbon, copper, hydrogen

Question 18

Compound

Answer 18

• two or more elements chemically combined
• components have a fixed ratio
• properties are different than the properties of the elements before chemical combination
  i. e.
• hydrochloric acid, baking soda, lye

Question 19

Heterogeneous

Answer 19

• can separate phases

i. e. Italian dressing, milk, sand

Question 20

Homogeneous

Answer 20

• called a solution
• one substance dissolved in another
• can’t see separate components
• mixed on the molecular level
  ie. air, brass, salt water

Question 21

Iron Content

Answer 21

Cereal, Nuts, Carrots contain the highest amounts of iron from our lab

• The absorbency of light was what determined the iron content, based on standard samples of specific concentration of iron.
• Iron is important to the production of hemoglobin in the blood which helps carry oxygen through out the body.

Question 22

Scatter Plots

Answer 22

The kind of graph we made in excel
R^2 value means the statistical measure that shows the relationship between the variables and their corresponding variables

Question 23

Slope

Answer 23

rise/run

y/x = y2-y1/x2-x1

Question 24

Independent Variable

Answer 24

variable that the experimenter is manipulating

Question 25

Dependent Variable

Answer 25

variable that changes as a result of, or depends on, what is happening to the independent variable.

Question 26

Rules of Graphing

Answer 26

1. Know your type (Bar, Line, Scatter)
2. Title the graph- should show the relationship b/w the variables
3. ind- x-axis and dep- y-axis
4. label axises
5. scale should be easy to plot and to read, equal increments- use more then half paper for the scale
6. include best fit line or curve displaying the formula.

Question 27

Interpolation

Answer 27

is an estimation of a value within two known values in a sequence of values.
i.e. determining breathe alcohol content

Question 28

Extrapolation

Answer 28

Using values already attained to find data points that would have been difficult to obtain in the lab. Used to predict further outcomes

Question 29

Direct

Answer 29

y value grows along with the x value

Question 30

Indirect

Answer 30

y values decrease as x values inc.