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Chemisty A level > Spectroscopy > Flashcards

Spectroscopy Flashcards

1
Q

What happens to an organic compound in a mass spectrometer?

A

it loses an electron and forms a positive ion - the molecular ion

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2
Q

What does a mass spectrometer detect?

A

the mass-to-charge ratio (m/z) of the molecular ion which gives the molecular mass

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3
Q

What is the molecular ion?

A

the positive ion formed when a molecule loses an electron

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4
Q

How do you determine the molecular mass from a mass spectrum?

A

the molecular ion peak is the largest no. peak

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5
Q

What is the symbol for the molecular ion peak?

A

M+

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6
Q

What is the M+1 peak?

A

a very small peak after M+ peak due to Carbon 13 or other isotopes

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7
Q

What is fragmentation?

A

in the mass spectrometer, some molecular ions break down into smaller pieces called fragments

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8
Q

What does fragmentation break a molecular ion up into?

A

a fragment ion and a radical

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9
Q

What is the m/z value of CH2OH+ fragment ion?

A

31

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10
Q

What is the m/z value for CH3+?

A

15

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11
Q

What is the m/z value for C2H5+ fragment ion?

A

29

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12
Q

What is the m/z value for C3H7+ fragment ion?

A

43

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13
Q

What is the m/z value for C4H9+ fragment ion?

A

57

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14
Q

What is the m/z value for CH3CH2O+ fragment ion?

A

45

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15
Q

How does infrared spectroscopy work?

A

covalent bonds posses energy and vibrate naturally
the amount of vibration increases with increasing temperatures
theses bonds can absorb infrared which makes them bend ans stretch more

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16
Q

What does the amount a bond streches or bends depend on?

A

the mass of the atoms in the bond = heavier—> slower vibration
the strength of the bond = stronger —-> faster vibration

17
Q

How does global warmbing occur due to IR radiation?

A

greenhouse gases absorb IR radiation because it has the same natural frequency of their bonds
the vibrating bonds re-emit this energy as radiation
resulting in increasing the temp of the earth

18
Q

What is infrared spectroscopy used for?

A

identifying the functional groups present in organic molecules

19
Q

What does an infrared spectrum show?

A

the frequencies that have been absorbed by the bonds

20
Q

What is the fingerprint region?

A

peaks below 1500 wavenumber - (dont need to indentify these peeks)

21
Q

What does an OH alchohol bond peak on infrared spectrum look like?

A

tall and broad, no spiking

22
Q

What does a C-H bond look like on an infrared spectrum?

A

small spikes

23
Q

What does a caroxyl OH infrared peak look like?

A

broad but has C-H spikes on the right side

24
Q

What is the application of infrared spectroscopy?

A

used to identify pollutants - CO, CO2 and hydrocarbons
breathalysers for the presence of ethanol

25
Q

What is element analysis?

A

use of % composition data to determine the empirical formula

26
Q

What is mass spectrometry?

A

use of the molecular ion peak from a mass spectrum to determine the molecular mass; use of fragment ions to identify sections of a molecule

27
Q

What is infrared spectroscopy?

A

use of absorption peaks from an infrared spectrum to identify bonds and functional groups present in the molecule

28
Q

Why is it important to maximise both atom economy and % yeild in industry?

A
  • high atom economy means that there is less/ no waste
  • high % yield means that raw materials are converted into desired products with minimum loss of materials
29
Q

What issues need to be considered when trying to maximise atom economy and % yield in industrial processes?

A

the cost of production = energy for heat
the toxicity of the reactant/ byproducts may be too risky to carry out the reaction

30
Q

What happens to molecules when they absorb IR radiation?

A

the bonds in the molecules vibrate

31
Q

What effect does CO2 and methane absorbing IR have on the environment?

A

it delays the escape of IR radiation by the earth into space = warms the atmosphere = greenhouse effect

32
Q

How has the conc of methane in the atmosphere risen?

A

intensive farming

33
Q

How has the conc of CO2 in the atmosphere risen?

A

burning fossil fuels

34
Q

What can be done to address global warming?

A

more efficient energy use = better insulation in homes
find alternative fuels = wind, solar, nuclear

Chemisty A level (28 decks)

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