Lab Techniques

Question 1

What are separations

Answer 1

Are a variety of lab techniques that use intermolecular forces to separate a mixture into its component parts.

Question 2

Name the four different separation techniques

Answer 2

Extraction
Distillation
Crystallization
Chromatography

Question 3

Describe the extraction technique

Answer 3

Is a separation technique based on solubility. “Like dissolves like”

1. Add a weak acid and shake
2. Add a strong acid and shake
3. Add a weak base and shake
4. Add a strong base and shake

Question 4

What is the phenol-chloroform extraction use for?

Answer 4

Is used to separate nucleus acids from cellular proteins.

Question 5

Distillation

Answer 5

Is a technique used to separate compounds that have significantly different boiling points. (20 degrees C) The compound with the lower boiling point will boil off first and can be captured and condensed in a cool tube.

Question 6

Fractional distillation

Answer 6

Is a more precise method of distillation that can be used to separate liquids whore boiling points are fairly close together. In fractional distillation the vapor is run through glass beads, allowing the compound with the higher boiling point to repeatedly condense and fall back into the solution.

Question 7

Crystallization

Answer 7

Is based on the principle that pure substances form crystals more easily than impure substances. Is a very inefficient method of separation. For most salts, crystallization is an exothermic process.

Question 8

Chromatography

Answer 8

Can be used to purify a compound from a mixture and it to identify the ratio of compounds in a mixture. It is the separation of a mixture by passing it over if through a matrix that absorbs (binds) different compounds more or less strongly according to their properties.

Typically the stationary phase is polar, causing more polar compounds to elute more slowly.

Question 9

Column chromatography

Answer 9

In Column chromatography, a solution containing the mixture is dropped down a column containing the solid phase (usually glass beads). The more polar compounds travel more slowly down the column, creating separate layers for each compound.

Question 10

High pressure liquid chromatography

Answer 10

Is one variant of column chromatography in which the column and solution use an apparatus that puts the system under high pressure.

Question 11

Paper chromatography

Answer 11

In paper chromatography, a small portion of the sample to be separated is spotted into paper. One end of the paper is then placed into a non-polar solvent. The solvent moved up the paper via capillary action. As the convent moves up the paper, the more polar component of the sample move more slowly bc they are attracted to the polar paper. The less polar component dissolve more easily to move up the paper with the solvent.

Question 12

Thin-layer chromatography

Answer 12

Is similar to paper chromatography except that a coated glass or plastic plate is used instead of paper, the results are visualized via an iodine vapor chamber.

Question 13

Gas-liquid chromatography

Answer 13

In gas-liquid chromatography, the liquid phase is the stationary phase. The mixture is dissolved into. Heated carrier gas (usually helium or nitrogen) and passed over a liquid phase bound to a column. Compounds in the mixture equilibrate with the liquid phase T different rates and lass through an exit port as individual components.

Question 14

Size- exclusion chromatography

Answer 14

Molecules are separated by their size and sometimes molecular weight, often through gel filtration.

Question 15

Ion exchange chromatography

Answer 15

Molecules are separated based on their net surface charge. This form of chromatography utilizes cationic or anionic “exchangers” that slow down the movement of charged molecules.

Question 16

Affinity chromatography

Answer 16

Uses highly specific interactions to slow down select molecules, rather than simply separating out all molecules that have a particular property. Affinity chromatography can make use of receptor-ligand, enzyme substrate, and antigen antibody interactions, among others.

Question 17

Gel electrophoresis

Answer 17

Can be used to separate mixtures of nucleus acids (DNA & RNA) or mixtures of proteins/polypeptides based on size and charge. Bc nucleus acids are negatively charged they migrate through the gel in response to the electric field. Larger particles move more slowly. After applying the electric field for an appropriate amount of time distinct bands can be visualized.

Question 18

Southern blotting

Answer 18

Is a technique used to identify target fragments of s known DNA sequence in s large pollution of DNA.

Question 19

Northern blot

Answer 19

Is just like a southern blot, but it identifies RNA fragments, not DNA fragments.

Question 20

Western blot

Answer 20

Is used to detect a particular protein in a mixture of proteins.

Question 21

How do you separate enantiomers from a racemic mixture?

Answer 21

3 ways…
1st uses differences in crystallization of the enantiomers.
2nd stereospecific enzymes are added to the mixture and will react with only one enantiomer, creating a compound that can be separated.
3rd enantiomers can be converted into diastereomers, which have different physical and chemical properties that can be used for separation.

Question 22

What is nuclear magnetic resonance spectroscopy?

Answer 22

(NMR) spectroscopy is the study of the interaction between atomic nuclei and radio ways. Is most commonly used to study hydrogen nuclei, but can be used to study the nucleus of carbon-13 and other atoms as well.

Question 23

IR spectroscopy

Answer 23

Uses molecular dipoles to find information about functional groups.

Question 24

Finger print region

Answer 24

600 to 1400 cm ^-1 region

Can be used to distinguish similar compounds.

Question 25

Ultraviolet region

Answer 25

Is much shorter than infrared light, between 200 and 400 mm, and is at a much higher energy level.

Question 26

Ultraviolet spectroscopy

Answer 26

Detects conjugated systems (double bonds separated by one single bond) by comparing the intensities of two beams of light from the same monochromatic light source.

Question 27

Mass spectrometry

Answer 27

Is used to determine a compounds molecular weight and in the case of high resolution mass spectrometry, it’s molecular formula.

Question 28

Base peak

Answer 28

Is the largest peak

Question 29

Parent peak

Answer 29

Is the peak made by the molecular ion.

Question 30

Name the IR absorption of these common functional groups.
O-H
C=O
C-H
N-H

Answer 30

O-H (3200-3600) broad
C=O (1710) sharp
C-H (2800-3000)
N-H (3300)

Question 31

Nucleus acid manipulation

Answer 31

DNA and RNA can be manipulated on a macro or micro level. Techniques can be used to join two strands together, pry two strands apart, chip one piece into smaller pieces, or join smaller pieces into a larger piece.

Question 32

Recombination and cloning

Answer 32

Many copies of be same piece of genetic material can be created and out in new places of otherwise manipulated.

Question 33

Sequencing and function techniques

Answer 33

Can be used to determine the exact nucleotide sequence of a piece of DNA or RNA. Additionally, a piece of nucleic acid that codes for a protein can be used to determine the function of that gene or protein.

Question 34

What does it mean to denature DNA

Answer 34

Means to separate the two strands of the double helix.

Question 35

What does t mean to hybridize DNA

Answer 35

Hybridization is going from 1 strand to 2 strands.