Chemistry - Vce Unit 3 - Spectroscopy And Chromatography

Front 1

What is chromatography?

Back 1

It is the separation of the components of a mixture based on differences in solubility and polarity.

Front 2

Types of chromatography

Back 2

Paper Chromatography
Thin-layer chromatography
Column chromatography (gas chromatography and HPLC)

Front 3

What is thin-layer chromatography (TLC)?

Back 3

Thin plate is coated in powder (stat. phase), mobile phase carries sample up the stationary phrase by capillary action, retardation factor of components allows identification of each components on the basis of characteristic polarity(Qualitative technique)

Front 4

What is column chromatography?

Back 4

It can be thought of as inverted TLC. Rather than traveling across a plate it runs down a column. stationary=a fine powder packed into the column
mobile=a solvent.
2 types - GC and HPLC

Front 5

What is gas chromatography?

Back 5

It requires the evaporation of a mixture, the vapors are passed through inert gas (mobile phase) and through a column with the stationary phase.

Front 6

What is high-performance liquid chromatography? (HPLC)

Back 6

It is done at high pressure with liquids as the mobile phase. The degree of absorbency of UV-light light indicates the flow rate of a compound. Identification and concentration can be found

Front 7

types of gas chromatography

Back 7

2 types gas liquid and gas solid
GL - stationary=high boiling point liquid supported by solid granules
GS - stationary=solid packed into column

Front 8

Spectroscopy is the ?
Spectrometry is the?

Back 8

Spectroscopy is the study of radiation absorbed or emitted by matter.
Spectrometry is the measurement of the amounts of light absorbed or emitted by matter

Front 9

wavelength is the ?
frequency is the?

Back 9

wavelength = distance between peaks
frequency = number of waves passing a given point each second

Front 10

How do atoms emit light?

Back 10

They absorb energy, electrons go into excited states, then return, emitting that energy in the form of light.

Front 11

Atomic emission spectroscopy (AES) involves

Back 11

Heated sample, light is passed through to produce line spectra. Position of lines gives ID- (qualitative) and strength of lines gives conc. relative to standard curve (quantitative but prone to errors)

Front 12

Atomic absorption spectroscopy (AAS) involves

Back 12

Light from cathode (chosen specifically) is pulsed through gas sample, bandspectra produced, black lines correspond to wavelengths absorbed. Position of lines gives ID (qualitative), strength of absorption gives conc. relative to a standard curve (quantitative).

Front 13

UV-visible spectroscopy involves

Back 13

Range of wavelengths passed through sample to produce graph, can be compared to others to identify sample (qualitative), one chosen wavelength strongly absorbed used to find conc. when standard curve has been constructed.

Front 14

Colorimetry uses a

Back 14

uses a complementary coloured filter to see how strongly the substances absorbs the light (subs. is blue, filter is yellow), used only to find conc.

Front 15

Infrared spectroscopy involves

Back 15

IF light passed through, wavenumber (1/wavelength) used to graph results, peaks correspond to functional groups present. Fingerprint region used for identification

Front 16

The fingerprint region

Back 16

in infrared spectroscopy, absorbance b/w 900cm^-1 and 1400cm^-1, used for identification because each molecule will show unique results in this region.

Front 17

Double beam spectroscopy

Back 17

Allows radiation to be continuously passing through sample and blank so they can be compared simultaneously

Front 18

In mass spectroscopy the sample is...?

Back 18

Vaporised, ionised, accelerated, deflected (according to mass-charge ratio), separated (by mass), and collected. Then mass and abundance are determined, results resented as mass spectrum.

Front 19

Mass spectroscopy is used to?

Back 19

Determine relative atomic masses and isotopic abundances of elements (to identify the element)
OR relative molecular masses of volatile compounds
(to identify structures of organic compounds)

Front 20

Mass spec calculations from isotopes and abundances

Back 20

%abundance X isotope(1) no. +% abundance X isotope(2) +... = Molecular mass (allows identification of element)

Front 21

Atomic Absorption Spectroscopy used to analyse what type of sample?

Back 21

Metals

Front 22

UV-visible Spectroscopy is used to analyse what type of samples?

Back 22

Substances that absorb light in the UV or visible regions of the electromagnetic spectrum
They can be coloured or colourless

Front 23

Colorimetry is used to analyse what types of samples?

Back 23

Substances with coloured solutions or a coloured solution produced by a reaction

Front 24

Infrared Spectroscopy is used to analyse what types of samples?

Back 24

Range of molecular substances, organic compounds containing functional groups

Front 25

Mass spectrometry is used to analyse what types of samples?

Back 25

Elements and compounds

Front 26

H1 NMR is used to analyse what type of sample?
C13 NMR is used to analyse what type of sample?

Back 26

Compounds containing hydrogen nuclei
Compounds containing carbon nuclei

Front 27

Nuclear Magnetic Resonance (NMR) used for?

Back 27

Determining precise structures of organic compounds.

Front 28

Theory of NMR

Back 28

When H1 nuclei are placed in magnetic field they spin in 2 different directions, if correct energy (radiowave) applied then spin-flip occurs, and exact wavelength at which energy absorbs depends on the strength of the magnetic field.

Front 29

In NMR the sample is ?

Back 29

Dissolved and placed in thin glass tube, placed in a strong magnetic field and irradiated with radio waves
The wavelength = constant
The strength of magnetic field =varied (sample is exposed to a range of strengths)

Front 30

In terms of NMR what does spin refer to?

Back 30

A property that H (and other) nuclei have
It means they spin and create a magnetic field like they are tiny magnets.

Front 31

NMR reference signal

Back 31

Is used because it's difficult to maintain exact magnetic strength, TMS is used because it is chemically inert and has 12 chemically equivalent nuclei, giving it a single sharp peak on the NMR, it absorbs at different wavelengths to most compounds so it doesn't interfere with their signals

Front 32

Low resolution NMR

Back 32

Number of peaks shows how many different environments, area under peaks shows proportion of each environment

Front 33

High resolution NMR

Back 33

Shows each peak split, according to the broader environment, that is, how many hydrogens are bonded to the next to the C it is bonded to (n+1 where n is the number of H bonded to the next C)

Front 34

When an electron spins, what does the spin create?

Back 34

A magnetic field.

Front 35

When does shielding and deshielding occur?

Back 35

If the magnetic field the electron creates reduces the strength of the applied field, the proton is shielded; if it enhances the applied field the proton is deshielded. Shielding creates an upfield shift, to the right, and deshiedling creates a downfield shift, to the left.

Front 36

What does the number of NMR signals represent?

Back 36

The number of different types of protons in a compound

Front 37

What is resonance (in regard to NMR)?

Back 37

A nucleus is in resonance when it absorbs RF radiation and "spin flips" to a higher energy state

Front 38

What is a spin flip?

Back 38

When a nucleus goes from being aligned with an external magnetic field absorbs enough energy to align itself against the magnetic field

Front 39

What is chemical shift?

Back 39

the position of the peak where a nucleus absorbs

Front 40

What does an NMR spectrum plot?

Back 40

The intensity of a peak against its chemical shift, which is measured in parts per million (ppm)

Front 41

What four different features of a proton NMR spectrum provide information about a compound's structure?

Back 41

1. Number of Signals
2. Position of Signals
3. Intensity of Signals
4. Spin-Spin Splitting of Signals

Front 42

Protons in different environments give ______ signals. Equivalent protons give the _____ NMR signal.

Back 42

Different
Same

Front 43

Where a particular proton absorbs depends on its electronic ______?

Back 43

Environment

Front 44

Why does shielding shift an absorption upfield?

Back 44

Shielding implies that an electron is decreasing the external magnetic field that the proton feels. Because the proton experience a lower magnetic field strength, it needs a lower frequency to achieve resonance. And lower frequency is to the right (upfield) in an NMR spectrum

Front 45

What can cause deshielding of a proton?

Back 45

A proton that is near an electronegative atom (like Cl or F). This is because they are electronegative elements and therefore pull electrons towards themselves