physical chem Flashcards
1
Q
isotopes
A
atoms of the same element with different number of neutrons
2
Q
Relative atomic mass (Ar)
A
the average mass of the atoms of the naturally occuring isotopes of an element relative to 1/12th the mass of a C-12 atom
3
Q
relative isotopic mass
A
4
Q
relative molecular mass (Mr)
A
5
Q
Relative formula mass
A
6
Q
Mole
A
7
Q
Avagadros constant
A
6.02*10^23
8
Q
A
9
Q
A
10
Q
A
11
Q
gdm-3 -> moldm-3
A
divide by mr
12
Q
n=
A
m/Mr
v/24
M*V
13
Q
M(gmdm-3)
A
m/V
14
Q
denisty=
A
m/v
15
Q
atoms consist of
A
a nucleus surrounded by electron shells
16
Q
the nucleus is made up of
A
protons, which are +ve charged and neutrons which are neutral and hence have no charge
17
Q
the electron shells are composed of
A
electrons that revolve around the nucleus, electrons are -vely charged
18
Q
in an atom the number of protons =
A
number of electrons
19
Q
the proton number is
A
the atomic number
20
Q
A
21
Q
ions
A
atoms that attain a charge after gaining or loosing electrons
22
Q
cations
A
+ve
23
Q
anions
A
-ve
24
Q
an idead gas is a gas that obeys
A
pV=nRT
25
in an ideal gas,
there are no IMF, the volume of particles is negligible compared to the volume of a gas
26
all collisions of ideal gas particles are
elastic
27
ideal gas particles move
rapidly and randomly
28
how does a gas approach ideal gas behaviour
as the temperature of the gas increases, as pressure of a gas decreases
29
pV=nRT units
p is pressure in pascals
V is volume in m^3
n is number of moles
R is 8.31
T is temperature in kelvin
30
pressure is inversely proportional to volume
31
when pressure increases
temperature increases
32
he is the
closest ideal gas
33
when we heat a solid the particles gain
energy hence they vibrate more strongly and the solid expands, when a solid is heated further beyond a certain point, the energy is enough to break the bonds or IMF in the solid and hence the particles move further apart and start sliding over each other forming a liquid, this is called melting
34
when we cool a liquid
the particles loose energy and hence come closer together as they move slowly the forces of attraction between the particles increase, bringing the particles even closer hence forming a solid, this is called freezing
35
when we heat a liquid
the particles start gaining energy and start moving faster, the liquid expands
36
evaporation
the particles with most energy at the surface tend to form a vapour and escape
37
boiling
when a liquid is heated further , there us enough energy to break the bonds or intermolecular forces inside the liquid so the particles move apart, forming a gas or a vapour the temp at which this takes place is called boiling point
38
enthalpy change of vaporisation
the energy needed to change one mole of liquid to one mole of gas
39
condensation
when we cool a gas, the particles loose energy and hence, they move closer to each other and move more slowly, this I because of increases forces of attraction between the particles, condensation also takes place at the boiling point
40
vapour pressure
when we heat a liquid in a closed container, some of it evaporates and moves up to the lid, on the lid as the particles are closer together, they experience increased forces of attraction, which results in the vapour turning back to the liquid on the lid, over time a dynamic equilibrium is established between the liquid and the vapour the pressure of the vapour at this equilibrium is called vapour pressure
41
vapour pressure increases as
temperature increases because the particles gain energy and move faster and hence collide more frequently and with more energy withe the balls of the container
42
the temp at which vapour pressure = atmospheric pressure is called the
boiling point
43
alloys are _ of metals
mixture
44
alloys are _ and __ than metals that they are composed of
harder and more rigid
45
why are alloys harder and more rigid than the metals that they are composed of
metals have atoms of different sizes so it becomes difficult for the metal layers to move
46
graphite is
a giant molecular structure
47
graphite is an _ of carbon
allotrope
48
allotropes are
different form of the same element
49
giant molecular structure
has continuous network of covalent bonds
50
in graphite each carbon
atom is covalently bonded to 3 other carbon atoms forming hexagonal rings, these rings are stacked on top of each other
51
graphite has _ MP
high because it is difficult to break the covalent bonds within the rings
52
graphite uses
it is slipperly and is used as lubricant because the layers can slide over each other as the forces between the layers are weak van der waals forces
53
graphite conducts
electricity because each carbon atom has one free electron and these free electrons form an electron cloud over the rings which allows electricity to be conducted thus graphite is used in electrodes
54
graphite is _
INERT
55
GRAPHITE, red lines are covalent bonds and blue lines are vander waals forces
56
diamond has a
giant molecular structure
57
diamond is _ of carbon
allotrope
58
in diamond each carbon atom
is covalently bonded to four other carbon atoms forming a giant 3D network structure thus diamond has a very high MP because a lot of energy is needed to break the covalent bond
59
diamond is amonth the _ known substance on earth
hardest
60
diamond does not
conduct electricity because it does not have any free electrons
61
diamond is
INERT
62
DIAMOND
63
SiO2 has
a giant molecular structure
64
SiO2
Silicon (IV) oxide
65
in SIO2 each silicon atom
is covalentlty bonded to 4 oxygen atoms and each oxygen atom is covalently bonded to 2 silicon atoms forming a giant 3D network structure like diamond SiO2 has a high MP and is very hard
66
fullerenes have
simple molecular structures
67
fullerenes have
simple molecular structures
68
fullerenes are _ of carbon
allotropes
69
fullerenes are
ball like or tube like structures with hexagonal and pentagonal rings of carbon atoms, each carbon atom is covalently bonded to 3 other carbon atoms
70
C60 has a low MP and BP
because there are weak van der waals forces between the ball like molecules for the same reason, they are quite soft they conduct electricity but to a lesser extent than graphite and are quite reactive
71
nanotubes are tubes of hexagonal rings of
carbon atoms, electricity is conducted over the long axis of the tubes
72
metals lose electrons to gain
stability
73
non metals gain electrons to gain
stability
74
in ionic bonding
a metal looses its valence electrons to a non metal
75
ionic bond
results in the formation of a strong electrostatic force of attraction between the metal cation and nonmetal anion
76
dot and cross diagrams of NaCl
77
a lattice
alternating arrangement of oppositely charged ions, held together by strong ionic bonds
78
properties of ionic compounds
- they are solid at room temperature
- high MP
- high BP
- high enthalpy change of vaporisation
79
ionic compounds are generally soluble in water
this is because when the ionic compound is added to water, water molecules form bonds with the ions on the surface of the lattice, these bonds replace the bonds within the lattice thus ions go into the solution
80
ionic compounds do not conduct electricity in solid state because
the ions are immobile in the lattice however when the compound is molten or dissolved in water, the ions are mobile so currents pass through
81
the larger the charge on the ion
stronger the bond , thats why MgO is stronger than NaCl
82
when 2 non metals react
both need to gain electrons to attain stability they do this by sharing electrons
83
covalent bonds
force of attraction between the nucleus and the shared pair of electrons
84
a single bond is formed when
one pair of electrons is shared between the covalently bonded atoms
85
a double bond is formed when
2 pairs of electrons are shared between the covalently bonded atoms
86
a triple bond is formed when
3 pairs of electrons are shared between the covalently bonded atoms
87
dot and cross of Cl2
88
dot and cross of O2
89
dot and cross of N2
90
electronegativity
the extent to which an atom covalently bonded to another atom attracts the bonded pair of electrons
91
electronegativity increases
across a period
92
electronegativity decreases
down the group
93
bond polarity
the unequal sharing of electron pairs between covalently bonded atoms, the centres of positive and negative charge do not coincide, the bond is said to be asymmetric
94
in a polar bond
one atom has a partial positive charge and one atom has a negative charge
95
dipole
when both atoms have a partial charge in polar bond
96
no difference in electronegativity
non polar bonds, electrons equally shared
97
AlCL3 is a
covalent compound
98
dot and cross of AlCl3
99
2 types of IMF
van der waals forces
hydrogen bonds
100
2 types of van der waals forces
instantaneous dipole induced dipole forces
permanent dipole-dipole forces
101
instantaneous dipole- induced dipole forces
these forces exist between non-polar molecules
they are the weakest type of IMF
the larger the molecule the stronger the ID-ID forces due to more surface contact points
the more the number of electrons in the molecule, the stronger the id-id forces
102
permanent dipole-dipole forces
these forces exist between polar molecules
these are stronger than id-id forces
103
hydrogen bonds
there are the strongest type of IMF
they only exist between molecules that have -OH, -NH groups and if the HF molecule is present
104
C-H
non dipole
105
most electronegative elements
F,O anf then N
106
covalent bonds result in the formation of
a simple molecular structure which are held together by IMF
107
Molecules that are held together by Vander Waals forces are usually
gases and have low MP, BP and entalpies of vaporisation
108
Molecules that are held together by hydrogen bonds are usually
have high MP, BP and entalpies of vaporisation
109
molecules that are held together by ID-ID forces are
insoluble in H2O but highly soluble in non polar solvents
110
molecules that are held together by Permanent induced - dipole dipole forces are
weakly soluble in water, weakly soluble in non polar solvents but highly soluble in polar solvents
111
molecules that are held together by hydrogen bonds are
highly soluble in water
112
simple molecular compounds do not
conduct electricity because they have neither mobile ions nor mobile electrons
113
water has a
high surface tension compared to other liquids because of hydrogen bonds
114
ice is less dense than water because
of longer hydrogen bonds between molecules of water than in the liquid itself, give ice a more open structure
115
in a molecule, there is repulsion between
pairs of electrons
116
the repulsion between the lone pairs is the
maximum
117
the repulsion between lone pairs and bond pairs is
slighty smaller
118
repulsion between bond pairs is
the smallest
119
linear
120
trigonal planar
like AlCl3
121
bent or angular
122
tetrahedral
like CH4
123
trigonal pyramidal
like NH3
124
H2O
125
TRIGONAL BIPYRAMIDAL
LIKE PCl5
126
octahedral
like SF6
127
sp^3 hybridised orbitals in tetrahedral, 109.5 degree
128
sp^2 hybridised orbitals in trigonal planar 120 degree
129
sp hybridised orbitals in 180 degree
130
bond energy
the energy needed to break one mole of a bond in gaseous state
131
as bond length increases
bond energy decreases
132
coordinate bond
one species provides both the electrons for the formation of a covalent bond, this type of covalent bond
133
coordinate bonds are AKA
dative covalent bonds
134
the strength of a coordinate bond is the same as that of a
covalent bond
135
NH4+ DATIVE COVALENT
136
AlCl3 and Al2Cl6 are
dimers
137
Al2Cl6 dot and cross
138
AlCl3 exists at
high temp
139
Al2Cl6 exists at
low temp
140
