Spectroscopy Flashcards Preview

Chemistry OCR A A level > Spectroscopy > Flashcards

Flashcards in Spectroscopy Deck (18)
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1
Q

What is mass spectra used for?

A

Identifying the molecular mass of a compound

Gaining further information about a compounds structure

2
Q

What happens when an organic compound is placed in a mass spectrometer?

A

Loses an electron and forms a positive ion

3
Q

What is the molecular ion?

A

The positive ion when a molecule loses an electron

4
Q

Where is the molecular ion peak located?

A

A clear peak at the highest m/z value on the far right hand side of mass spectrum

5
Q

Why do some molecules have a small peak after the molecular ion?

A

They have a small proportion of carbon-13 present in the molecule

6
Q

What are fragment ions?

A

Peaks in mass spectrum formed from the break down of the molecular ion

7
Q

What two species does simple fragmentation break a molecule into?

A

A positive ion and a radical

8
Q

What does absorbing IR do to covalent bonds?

A

Makes them stretch and bend more

9
Q

Why do molecules stretch?

A

To increase the distance between the atomic centres

10
Q

What 2 factors affect how much a bond stretches or bends?

A

Mass of the atoms in the bond

Strength of the bond between atoms

11
Q

What is the only radiation a bond can absorb?

A

Radiation that has the same frequency as the natural frequency of the bond

12
Q

Explain how the ‘Greenhouse Effect’ works?

A

Sun’s visible light and IR radiation passes into the Earth’s atmosphere
Earth absorbs radiation
Some radiation re-emitted in the form of IR
Greenhouse gases(GG) absorb this radiation as same frequency as there natural bonds
Vibrating bonds in GG’s re-emit radiation that heats up atmosphere

13
Q

What are the 3 most common greenhouse gases?

A

Water Vapour, Carbon Dioxide, Methane

14
Q

Explain the 4 steps of how IR spectroscopy works

A

1) Sample placed in IR spectrum
2) A beam of IR radiation in range 200-4000 is passed through sample
3) Some radiation absorbed and emerging beam of radiation identified what has been absorbed
4) Graph of transmittance against wave number produced

15
Q

Where does the finger print region occur?

A

Below 1500cm^3

16
Q

What is the finger print region and how is it used?

A

An area in which the exact molecule can be determined due to unique peaks
Uses computer software or comparing booklets to published spectra

17
Q

What are two key applications of mass spectrometry?

A

Breathalysers

Break down of pollutants present in the atmosphere

18
Q

What are 3 processes used in molecule identification?

A

Elemental Analysis
Mass Spectrometry
IR spectroscopy