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CHEM1603 CH > Section A > Flashcards

Section A Flashcards

1
Q

What is the most abundant element in the human body?

A

Oxygen at ~65%, present in water, lipids, carbohydrates

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2
Q

What is the second most abundant element in the human body?

A

Carbon at ~18% of your mass, key in proteins, sugars, lipids

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3
Q

What is the spin of an electron/proton/neutron?

A

All are 1/2 spin

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4
Q

What varies in an isotope, and what can we use to measure this?

A

Neutron number varies, mass spectrometer used to measure

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5
Q

What is the mass in Kg of one atomic mass unit (AU)?

A

1.6605 x 10-27Kg

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6
Q

What is the definition of a mole?

A

A substance containing Avogadro’s number of molecules, 6.022 x 1023

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7
Q

What is Avogadro’s number (NA)?

A

6.022 x 1023

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8
Q

What is the Aufbau principle?

A

Principle of ‘building up’ of electron shells, electrons occupy lower energy orbitals first

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9
Q

What is the Pauli exclusion principle?

A

No 2 electrons can have the same 4 quantum numbers

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10
Q

What is a wave function?

A

Mathematical description of distribution of an electron in terms of position and time

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11
Q

What is the uncertainty principle?

A

Position and momentum cannot simultaneously be determined

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12
Q

What defines an orbital?

A

Region of space where where an electron is most likely to be located

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13
Q

What are the names of the four quantum numbers?

A

Principle, Angular momentum, magnetic, electron spin

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14
Q

How does the principle quantum number (n) define the nucleus and what values may it take?

A

Tells you how big the orbital is e.g. which shell the electron is orbiting in, values: 1 to infinity

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15
Q

How does the angular momentum quantum number (I) define the nucleus and what values may it take?

A

Tells you about the shape of the orbital, I value always 1 smaller than n value (n-1), stands for 3 sub shells, s (0) p (1) and d (2)

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16
Q

What shape is an s sub shell?

A

Spherical

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17
Q

What shape is an p sub shell?

A

figure of 8 shaped

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18
Q

What shape is an d sub shell?

A

like a 4 blade propellor

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19
Q

How does the magnetic quantum number (mi) define the nucleus and what values may it take?

A

Tells you the orientation of the orbital, s can only have one orientation, p has 3 -> px (-1), py (0) and pz (1) -> d-orbital -2 -> 2

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20
Q

What is the radial distribution function?

A

How probability of finding electrons varies from nucleus

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21
Q

What is a position around the nucleus where function = 0 called?

A

node

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22
Q

Why are 2 electrons allowed to occupy one orbital?

A

Due to different spin numbers, one spin up and one spin down electron is allowed

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23
Q

What is Hund’s Rule of Maximum multiplicity?

A

if 2 or more orbitals have same energy, then electrons will spread out to occupy maximum possible number of these, maximising number of parallel spins

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24
Q

What is spin correlation?

A

Parallel spins will stay further from each other to reduce electrostatic repulsion

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25
Q

What metal is present in , and vital for the function of Vitamin B12?

A

Cobalt, has 3 stable oxidation states close to one another, break Co-C bond diff. ways

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26
Q

At what point are a pair of atoms considered to have a chemical bond between them?

A

When atoms lie in ‘energy well’, have a lower potential energy than individual atoms

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27
Q

Define covalent bonding

A

Covalent bonding is when valence electrons are shared between 2 atoms

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28
Q

What is the octet rule?

A

Each atom shares electrons until it’s valence shell contains 8 electrons

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29
Q

What is a Resonance Hybrid?

A

Average lewis structure made from different resonance forms

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30
Q

What is a hypervalent compound?

A

A lewis structure which requires more than an octet of electrons e.g. PCl5

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31
Q

What are the basic assumptions of Valence shell electron repulsion theory (VSEPR)?

A

electrons from bonds/lone-pairs are considered as charge clouds, lowest energy arrangement = far apart as possiblee

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32
Q

What are further assumptions of the VSEPR theory?

A

lone pairs repel more than bonding pairs, multiple bond treated as single electron pair, lone pairs favour equatorial site

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33
Q

What importance does molecular shape have in biology?

A

enzyme active site, cell receptors, antibody/antigens

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34
Q

What are the limitations of VSEPR?

A

Cannot explain hyper valency or paramagnetism

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35
Q

What is Valence bond theory?

A

bonding orbital created by overlapping of 2 half filled atomic orbitals

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36
Q

What is hybridisation?

A

different atomic orbitals combining to give the same amount of equivalent hybrid orbitals

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37
Q

The hybridisation theory was proposed by which scientist?

A

Linus Pauling

38
Q

What bond is formed in SP3 hybridisation?

A

Single bond, 3 types of bonding

39
Q

What bond is formed in SP2 hybridisation?

A

Double bond, only 2 different types of bonding

40
Q

Define a sigma bond

A

lie along line between atoms, symmetrical to rotation around bond, occur between s (and p and d) orbitals

41
Q

Define a pi bond

A

overlap sideways on, not symmetric to rotation around the bond, occurs between p orbital

42
Q

What are the benefits of valence bond theory over VSEPR?

A

Useful for discovering bond length/strength/force constant, acid base interactions, bond polarity

43
Q

What are the issued of valence bond theory?

A

Still cannot explain paramagnetism in O2

44
Q

What principle of electron behaviour does molecular orbital theory exploit?

A

Wave like nature of electrons, combinations of waves can be destructive/constructive, gives the bonding/antibonding orbitals

45
Q

What denotes an anti bonding orbital?

A

A * sign

46
Q

In an antibonding molecular orbital, is there 1 or 2 orbitals?

A

1, there is a node in the centre which causes orbital to look separate

47
Q

After atomic orbitals have combined, is the bonding or anti bonding orbital of higher energy?

A

Antibonding orbital has a higher energy than bonding orbital and original orbitals

48
Q

Will orbitals of different energies combine in the MO theory?

A

No, electrons must have the same angular momentum and principle quantum numbers

49
Q

What suggest favourable bonding in MO theory?

A

Electrons are in lower energy state in bonding orbital than they were in atomic orbital

50
Q

If there were equal numbers of electrons in the bonding and anti bonding MOs would a bond be favourable?

A

No, bonding would not be favourable because no energy gain having equal number of electrons in bonding/antibonding

51
Q

What is the equation for bond order?

A

[(no. bonding electrons) - (no. antibonding electrons)]/2

52
Q

What would a bond order of 0 suggest?

A

No bond favourable

53
Q

What would a bond order of 1 suggest?

A

Single bond favourable

54
Q

What effect would there be on the bonding/antibonding orbitals by a higher degree of overlap between atomic orbitals?

A

Bonding orbital would become lower, anti bonding orbital would become higher, bond strength would increase

55
Q

What type of bonding does the pz orbital undergo in MO theory?

A

Sigma bonding

56
Q

What type of bonding do the px and py orbitals undergo in MO theory?

A

Pi bonding

57
Q

What does LUMO stand for?

A

Lowest unoccupied molecular orbital

58
Q

What does HOMO stand for?

A

Highest occupied molecular orbital

59
Q

How does MO theory show paramagnetism in O2?

A

Shows 2 unpaired electrons in 1 pi* orbital

60
Q

Are covalent or non covalent bonds ‘highly directional’?

A

Covalent bonding is highly directional

61
Q

Which of bonding (covalent/non-covalent) forms longer lasting, but shorter bonds?

A

Covalent

62
Q

What type of bonding (covalent/non-covalent) can form inter and intra molecular bonds?

A

Non-covalent

63
Q

What are the 6 types of non-covalent bonds?

A

London dispersion, Dipole-Dipole, Dipole-induced-Dipole, Ion-Dipole, Ion-Ion, Hydrogen

64
Q

What symbol is used to represent polarity between atoms in VDW forces?

A

An arrow with a plus at the delta positive atom, and the arrow head faced toward delta negative atom

65
Q

What causes polarity in a bond?

A

Electronegativity

66
Q

How does electronegativity of atoms vary across a period?

A

Increases as you go across period (N is most electronegative)

67
Q

How does electronegativity of atoms vary down a group?

A

Decreases as you go further down group

68
Q

Is a high bond polarity likely to mean a covalent or ionic bond is formed?

A

Ionic

69
Q

What is the overall molecular dipole moment (mu)?

A

The sum of individual bond dipole vectors in a molecule

70
Q

Would dipoles of neighbouring molecules interact?

A

Yes, they would attract each other, gives rise to VDW forces

71
Q

What’s the equation for the overall interaction energy between dipolar molecules?

A

E = -1/r^6 (r = distance)

72
Q

What is a dispersion interaction?

A

Instantaneous dipole induces dipole in neighbour, dipoles attract

73
Q

What is polarisability?

A

Ability of an atom to become polarised

74
Q

Why does Br have a higher boiling point than Cl?

A

Br is more polarisable, so stronger dispersion interactions in neighbours

75
Q

What is the dielectric constant otherwise known as?

A

Relative permittivity

76
Q

What is the dielectric constant?

A

The ability of a material to store electrical energy when exposed to an electrical field, more polar molecules = higher dielectric con.

77
Q

Is the dielectric constant a property of an individual atom or a bulk substance?

A

Bulk substance

78
Q

What is the relationship between dipole moment, polarity and dielectric constant?

A

Greater dipole moment = more polar = higher dielectric constant

79
Q

What happens to dipoles in hydration of ions?

A

Dipoles align in the field of the ion, lowers self energy of ion and stabilises

80
Q

What is the definition of a hydrogen bond?

A

2 strongly electronegative atoms, one bound to a hydrogen and one with a lone pair of electrons -> short ranged, strong

81
Q

Why does ice float on water?

A

When water freezes, molecules held apart by strong & stable H bonds -> further apart

82
Q

What is the Grothuss Mechanism?

A

covalent and hydrogen bonds can interchange, causes charge transfer, no diffusion of H+

83
Q

What is the benefit of the Grothuss mechanism?

A

Allows very fast conduction of H+ through water

84
Q

What is the stationary phase in TLC?

A

SiO2 layer on plate (silicon dioxide)

85
Q

What is another term for solute in chromatography?

A

Analyte

86
Q

What is TLC used for?

A

Separating compounds based on their different bonding/polarities, stronger reactions= shorter distance travelled

87
Q

What is the lifetime of a hydrogen bond?

A

1 - 10picoseconds (-12)

88
Q

What is the collecting together of non-polar molecules known as?

A

The hydrophobic effect

89
Q

Why does the hydrophobic effect occur?

A

Fewer ways of arranging hydrogen bond network when hydrophobic molecule added, reduces entropy, unfavourable for non-polar molecules to be surrounded by water - clump

90
Q

Define an amphiphile

A

molecule which contains polar and non-polar areas (hydrophillic & hydrophobic)

CHEM1603 CH (6 decks)

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