Chemistry Lab Final Exam

Chromatography is a versatile physical method separation and characterization by which two or more components in a mixture are distributed between two phases: stationary and moble.
The attachment of molecules to the surface of a solid
Thin Layer Chromatography (TLC)
is a specialized form of chromatography. It is a simple, sensitive and quick technique for analyzing and separating ultra small quantities of organic compounds. It is used specifically to check the purity of a compound, to determine the number of components in a mixture, to evaluate the progess of a chemical reaction, and to analyze the composition of a mixture.
implies penetration of melecules into the solid
Applications/ benefits of chromatography
evaluating air quality
determining pesticide residues on fruits and vegetables
monitoring respiratory gases during anesthesia
searching for organic compounds on other planets
determining metabolic pathways and mechanisms of action of drugs
detecting and solving crimes
Know how we were able to see the separation of the analgesics even though they are all colorless.
We put it under a UV light and traced the spots
why do some components travel further than others?
Small molecules more faster than large molecules.

The more soluble the solution, the fater it is carried up, the less soluble it is makes it stay and the liquid will pass right through

what is an rf value and how do you determine it.
The distance traveled by each component is expressed as a rate or retention factor (Rf)
Rf= distance traveled by an ingredient/ distance traveled by the solvent (measured from origin point where the spot was initially applied to the plate)
How is chromatography used to identify substances?
The composition of the unknown substance (medication) is determined based on matching retention factor (Rf) values and solute spots for the known substances (medications)
In the TLC lab, which active ingredient moved the farthest distance? Why?
Ibuprofin moved the fartherst b/c it has smaller molecules, has a low affinity and is most soluble
In the TLC lab, which active ingredient moved the shortest distance? Why?
The 2nd unknown moved the shortest distance (acetaminophen) b/c is has the largest molecules, has a high affinity, and is less soluble
In the TLC lab, what was the purpose of placing a piece of filter paper in the developing chamber?
To keep the atmosphere within the glass block saturated w/ solvent vapors at all times
In the TLC lab, in order to identify an unknown analgesic using TLC, a sample of a known analgesic (a standard) must be spotted on the same plate as the unknown. Why is this necessary?
So you have something to compare it to
In the TLC lab, why did you cover the TLC chamber with a watch glass or glass cover?
So the solvent couldn’t evaporate
In the TLC lab, why is it important that the spots on the TLC plate be made as small as possible (less than 2 mm in diameter)?
Larger spots will tail and overlap themselves
Can you use TLC to determine if a cup of coffee is caffeinated or not?
Yes, if you saturate a spot w/ caffeine and saturate another spot w/ the coffee, you could see the similarities of each and compare their movement up the TLC plate
In the TLC lab, what problem might be encountered with the following experimental procedures:

A single micropipet was used to stop four analgesic samples of a TLC plate

Cross contamination of substances
In the TLC lab, what problem might be encountered with the following experimental procedures:

Using a TLC plate which was marked with ink

The ink would contaminiate the plate and could cause different results
In the TLC lab, what problem might be encountered with the following experimental procedures:

A TLC plate touching the filter paper liner of the development chamber

The spots of solution could rub off onto the filter paper
In the TLC lab, what problem might be encountered with the following experimental procedures:

The depth of the solvent is above the levol of the spots

The results would be wrong b/c the spots wouldn’t travel up the plate, but instead stay at the bottom

Fe3O—-> 3 Fe + 2 O2


How would you classify this reaction?


 AgNO3(aq) + NaCl (aq) —-> NaNO3(aq) + AgCl (s)


How would you classify this reaction?

Double replacement

2 Ag NO3(aq) + Cu(s) —-> Cu (NO3)2(aq) +2 Ag


How would you classify this reaction?

Single replacement

C(s) + O2(g) —-> CO2 (g)


How would you classify this reaction?

Sodium Chloride
barium nitrate
hydrochloric acid
sodium hydroxide
sodium carbonate
acetic acid
barium chloride
potassium sulfate
iron(II) sulfate
potassium hydroxide
magnesuim oxide
copper(II) sulfate
iron (III) hydroxide
potassium nitrate
zinc chloride
carbon dioxide
iron(III) nitrate
silver nitrate
silver chloride
calcium sulfide
How can you determine if a chemical reaction has occurred?

1. formation of precipitate (change in solubility)

2. evolution of gas

3. change in color

4. change in odor

5. change in temmperature

Determine the product of this reactant:


NaCl(aq) + Ba(NO3)2 —-> ?

NaCl(aq) + Ba(NO3)2 —-> 2NaNO3 + BaCl2

Determine the product of this reactant:


HCl(aq) + NaOH(aq) —-> ?

HCl(aq) + NaOH(aq) —-> NaCl + H2O

Determine the product of this reactant:


Na2CO3(aq) + HC2H3O2(aq) —-> ?

Na2CO3(aq) + HC2H3O2(aq) —-> NaC2H3O2 + H2O + CO2
what factors determine how quickly a reaction occurs?
concentration and temperature

Determine the product of this reactant:


BaCl2(aq) + K2SO4(aq) —-> ?

BaCl2(aq) + K2SO4(aq) —-> BaSO4 + 2KCl
Increases OH- concentration in solution (8-14)

Determine the product of this reactant:


CuSO4(aq) + NH4OH(aq) —-> ?

CuSO4(aq) + NH4OH(aq) —-> Cu(OH)2 + (NH4)2SO4
What are the 4 different product formations?

1. precipitation

2. neutralization (A/B)

3. Redox

4. Gas-forming

The study of how fast or slow a reaction occurs
Increases H+ concentration in solution
What must take place in order for a chemical reaction to occur?
Reactants must collide effectively and then combine to form new cubstances. Consequently, the greater the number of particles (the higher the concentration) and the higher the temperature (the more rapid and more energetic the motion of the particles), the faster the reaction
Know what color litmus paper turns in the presence of an acid and a base.
Acid: Red
Base: Blue
Is HCl and acid or a base?
Is NaOH an acid or a base?
What is phenolphthalein and what color does it turn when it is in an acid and a base?

Color in acid:clear
Color in base: pink

Give some examples of acids and bases
Acids:Lemon juice, pineapple juice, tomato juice, grapefruit juice, clorox-2, vinegar, lysol, sugar, soda pop

Bases: Liquid drano, baking powder, baking soda, bleach, ammonia, milk of magnesia, nair

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