chem Flashcards
(167 cards)
1
Q
what trend is there in atomic radius as we move left to right across a period? why?
A
decreases
increased nuclear charge which pulls electrons closer
2
Q
what trend is there in 1st ionisation energy as we move left to right across period three? why?
A
increases
increased nuclear charge means more energy needed to remove electrons
3
Q
what are the chemical formulae of phosphorus, sulphur and chlorine
A
P4
S8
CL2
4
Q
as we move across period three why is the 1st ionisation energy of S lower than P despite an increase in nuclear charge
A
Sulphur has 2 of its 3p electron paired, while phosphorus does not. the paired electrons repel.
5
Q
what type of structure does phosphorus, sulphur and chlorine have
A
molecular
6
Q
which element in period two, lithium to neon would have the highest 2nd ionisation energy
A
lithium
because the electron is being removed from the 1s sub shell which is closer to the nucleus and experiences less shielding so is harder to remove an electron
7
Q
why are 2nd ionisation energies greater than 1st ionisation energies?
A
takes more energy to remove an electron from a positive ion
8
Q
as we move across period 3 why is the 1st ionisation energy of Al lower than Mg despite an increase in nuclear charge?
A
electron being removed from higher energy sub-shell. 3s in Mg and 3p in Al
9
Q
what trend is there in melting and boiling point within period 3? why?
A
increases Na-Al as the charge of positive metal ions increases.
for the non metals strength of van der waals forced, governed by size of molecules mean S>P>Cl>Ar
Si has highest as its giant covalent
10
Q
write an equation for the first ionisation energy of E
A
E(g) -> E+(g) + e-
11
Q
what type of structure does silicone have
A
macromolecular
12
Q
why does temp not increase while a substance is melting or boiling
A
the energy is absorbed as the bond weakens
13
Q
what effects the strength of a permanent dipole-dipole force
A
the bigger the difference in electronegativity between a bonding pair the greater the diploe so the greater the force
14
Q
starting with the weakest, name the 3 types of intermolecular attraction
A
van der waals
permanent dipole-dipole
hydrogen bonding
15
Q
what can we say about the polarity of bonds between different elements
A
they will be polar to different extents depending on the elements
16
Q
what are giant covalent bond held together by
A
covalent bonds
17
Q
what can we say about the polarity of bonds in elements
A
they are not polar
18
Q
what are molecular crystals held together by
A
intermolecular force hold molecules together covalent bonds hold the atoms within molecules together
19
Q
what is a dative covalent bond
A
a shared pair of electrons, where both have been supplied by one atom
20
Q
what is meant by a polar bond
A
where the charge is not symmetrical, so one area is more positive and one area is more negative
21
Q
what causes permanent dipole-dipole forces
A
attraction between molecules with permanent dipoles
22
Q
what causes a hydrogen bond
A
when hydrogen covalently bonds to N,O,F. the H can be shared with this or a lone pair of another electron
23
Q
what are ionic crystals held together by
A
electrostatic attraction between oppositely charged particles
24
Q
what are the four types of crystal structures
A
ionic, metallic giant covalent and covalent
25
where do we find van der waals and what effects its strength
found in all atoms and molecules. the more molecules the bigger the force
26
how do we convert cm3 to dm3
divide by 1000
27
if we make a change to conc. temp. or pressure how will the equilibrium respond
it will move to reduce the disturbance
28
why might a compromised temp be used
a high temp will decrease the % of product at equilibrium
| a low temp will mean that equilibrium is reached to slowly to be economically viable
29
other than yield why might a compromise pressure be used
cheaper
30
why do haber process plants run at a higher temp and lower pressure that would produce the maximum conversion
high temp = faster
| low pressure = less expensive
31
ammonia
NH3
32
what is 80% of ammonia used to make
fertilisers
33
define molecular mass
the average mass of a molecule compared to 1/12th the mass of an atom od C-12
34
what equation links moles, conc, and volume
n=cxv/1000
35
define relative atomic mass
the average mass of an atom compared to 1/12th of the mass of C-12
36
what effect does a catalyst have on the position of equilibrium
none
37
write an ionic equation to summarise NaOH+HCL -> NaCL=H2O
H+(aq) + OH-(aq) -> H2O (l)
38
what is the difference between dynamic equilibrium and equilibrium
equilibrium means hat the conc. of reactants and products are unchanged, addition of the word dynamic means the reaction is still preceding while the situation exists
39
what is methanol used for
motor fuel
| starting material
40
what is ethanol made from ethane used for
making cosmetics, drugs, inks, detergent
41
give the chemical reaction for the hydration of ethane to form ethanol
C2h4 + h2o -> c2h5oh
42
what is the equation for calculating % yield
(actual yield/ theoretical) x100
43
how do you convert from empirical formula to molecular formula
work out mass of the empirical and molecular formula. divide empirical by molecular. multiply the number by each element in the empirical formula
44
what is an equilibrium mixture
the mixture of chemicals found in a dynamic equlibrium
45
what is the equation used to calculate % economy
molecular mass of desired product/sum of all molecular masses x100
46
what is empirical formula
the simplest ratio of atoms of each elements in a compound
47
what is a reversible reaction
a reaction which can proceed in either direction between reactants and products
48
in the context of heterogeneous and homogeneous what is a phase
different physical state
49
what are the two catalysts what do they mean
homogeneous- same phase
| heterogeneous- different phase
50
how do catalyst work
they provide an alternative route for the reaction, with a lower activation energy
51
what effect do catalysts have on the position of equilibrium for reversible reactions
none
52
what is the meaning of the term catalyst
something that alters the rate of a chemical reaction, but is not used up in the reaction
53
what does increasing the conc. increase the rate of reaction
makes collisions more likely
54
why does temp have such a big impact on rate
temp increases the number of particles with energy above the activation energy
55
on a M-B distributions, where is the average energy in reletion to the most probable
right
56
do most collisions between particles result in a chemical reaction why
no
| they may not have enough energy or the wrong orientation
57
five factors that effect rate reaction
```
temp
conc
pressure
surface area
catalyst
```
58
what is the catalyst in a catalytic converter in a honeycomb shape
to provide a much greater surface area
59
define activation energy
minimum amount of energy to start a reaction and break bonds
60
do any particles in a gas have 0 energy
no
61
what are zeolites
minerals with a very open pore structures that ions or molecules can fit into. they are used as catalysts
62
what does collision theory tell us
that reactions can only occur when collisions take place between particles that have enough energy
63
what effect to catalyst have on enthalpy change for reactions
none
64
what does the prefix 'di' mean
two of them
65
what does the production of greenhouse gases contribute towards
global warming
66
why do we crack hydrocarbons
to produce smaller molecules that are higher in demand
67
what is empirical formula
the simplest whole number ratio in which atoms in a compound combine together
68
what greenhouse gas, does burning fossil fuels release into the atomosphere
CO2
69
what does a negative sigh infront of delta H mean
forward reaction is exothermic
70
name a catalyst used in a catalytic converter
platinum or rhodium
71
give the equation for the reaction of carbon monoxide with hydrogen to form methanol
CO + 2H2 -> CH3OH
72
how do you convert concs. from gdm-3 to moldm-3
divide by molar mass
73
what is meant by agravados constant
number of partials in a mole.
74
how does fractional distillation work
crude oil is heated, it is hotter at the bottom and coolest at the top vapours pass up the tower through tray with bubbles caps. when they arrive at a tray that is sufficiently cool they condense into a liquid where they are piped off
75
what are the 1st six prefixes of organic molecules
```
meth
eth
prop
but
pent
hex
```
76
where do we collect shorter chain hydrocarbons from in a fractionating tower
near the top
77
where we have more than one functional group, how do we decide which one to write first
functional groups go in alphabetical order
78
what does cracking do to the c-c bonds in alkanes
breaks them
79
what do we call a hydrocarbon with a =
alkene
80
when writing out names of molecules, where do we put a hyphen
between names and numbers
81
what problems might carbon produced by incomplete combustion have on health and the environment
asthma, damages lungs and global diming
82
what do we call the thick residue that collects at the bottom of the fractioning tower
tar/ bitumen
83
what is meant by displayed formula
a formula of a compound drawn out so that every carbon atom and every bond is shown
84
what homologous series is petroleum mainly made of
alkanes
85
what are the conditions and main products of thermal cracking
high temp
high pressure
high percentage of alkenes
86
what issues are there with burning a fuel that contains sulfur
sulphur dioxide will be produced that causes acid rain
87
what amount of energy do most particles have? how can we find this from a M-D distribution
an intermediate amount of energy at the peak of the curve
88
what are functional group isomers
where isomers have different functional groups
89
what are the 3 types of structural isomers
chain, position, functional group
90
what are positional isomers
where the functional group in isomers is attached to the main chain at different points
91
how is sulphur dioxide removed from flue gases
using CaO
| this reacts with the SO2 to produce CaSO4 which is used as plaster
92
where must a reaction be in order for a dynamic equilibrium to be reached
a closed system
93
what can we say about the proportion of reactants and products at equilibrium
any ratio not 50;50
94
how do we remove the pollutants produced by the internal combustion engine
using a catalytic converter
95
when moving left to right across period 3, what exceptions are there for the trend in increasing 1st ionisation energy? why?
aluminium- electron removed by 3p
| sulphur- two electrons in 3p so repulsion occurs
96
what are alkanes
saturated hydrocarbons
97
what two products are produced by the complete combustion of hydrocarbons
carbon dioxide and water
98
what is meant by molar volume
1 mole of any gas takes up 24000 of space at room temp and pressure
99
what is meant by homologous series
a set of organic compounds with the same functional group
100
what is meant by functional group
an atom or group of atoms in an organic molecule which is responsible for the characteristic reactions of that molecule
101
what is meant by structural formula
a way of writing out an organic formula in which bonds are not shown but each carbon atom is written separately with the atoms or groups attached to it.
102
what is structural isomerism
where molecules have the same molecular formula, but a different structural formula
103
what are the conditions and main products of catalytic cracking
slight pressure
high temp
zeolite catalyst
104
what are chain isomers
where the hydrocarbon chain in isomers is arranged differently
105
what products would we expect from the incomplete combustion of a hydrocarbon
carbon monoxide and water
106
what is le chateliers principle
if a system in equilibrium is disturbed, the equilibrium moves in the direction that tends to reduce the disturbance
107
in practice what conditions are used for producing methanol from carbon dioxide and hydrogen
500K
| 10,000kPa
108
what is the equation for the Haber process
N2 + 3H2 2NH3
109
what temp and pressure is used in most plants for the haber process
20,000kPa
| 670K
110
what do we call the process of reactants sticking to the surface of a catalyst
adsorption
111
which catalyst is used in the production of ethanol from ethene
phosphoric acid absorbed on silica
112
in practice, what conditions are used to produce ethanol from ethene
570K
| 6500kPa
113
what do we call the process of breaking away from the surface of a catalyst
desorption
114
what type of structure does argon have
atomic
115
what happens to the total area under a M-B distribution curve when the temp is changed
no change
116
what causes Van Der Waals forces
caused by instantaneous dipoles. these occur because in any instant electrons are not spread evenly and more will be in one another.
117
what do we call a hydrocarbon with a group 7 element attatched
halo- alkane
118
what can we say about a reaction in dynamic equilibrium
in a closed system, the rate of the forward and reverse reactions are the same so conc. is same
119
what are alkanes mainly used for
fuels
120
what happens to the boiling point of alkanes as chain length increases
increases
121
name 3 greenhouse gases
CO2
methane
water vapour
122
in terms of electrons, what is oxidation and reduction
Oxidation is loss of electrons
| Reduction is gain of electrons
123
what does an oxidising agent do in terms of electrons
accept electrons
124
what does a reducing agent do in terms of electrons
donate electrons
125
what is the oxidation state of hydrogen
+1 except in metal hydrides where it is -1
126
what is the oxidation state of Group 1
always +1
127
what is the oxidation state of Group 2
always +2
128
what is the oxidation state of Group 3
always +3
129
In the thermite reaction Fe2O3 + Al -> Fe + AlsO3. what is oxidised and what is reduced
Fe is reduced from +3 to 0
| Al is oxidised from 0 to +3
130
what are the 3 nucleophiles used in nucleophilic substitution reaction
Hydroxide
Cyanide
Ammonia
131
why is excess ammonia used in nucleophillic substitution reaction
to reduce the chance of the amine taking part in further substitution reactions
132
what are elimination reactions
when haloalkanes can react with hydroxide ions in an alternative mechanism. instead of producing an alcohol we produce an alkene
133
what happens if you react sodium/potassium hydroxide with a haloalkane
both nucleophillic substitution and elimination reactions.
134
how do you favor an elimination reaction
> concentrated NaOH/KOH
> ethanol as solvent
> high temp
135
how do you favor nucleophillic substitution reaction
> more dilute NaOH/ KOH
> water as solvent
>Low temp
136
what do the hydroxide ions act as in elimination reactions
a base
137
what do the hydroxide ions act as in nucleophillic substitution reactions
a nucleophile
138
what is critical for E/Z isomerism to exist
A must not = B and C must not = D
139
E isomerism
>trans
| > opposite look like a Z
140
Z isomerism
> cis
| > next to look like a E
141
what do electrophillic addition reactions happen with
> Halides eg HBr and HI
> Bromine
> H2SO4
142
what is a reducing agent
electron donor
143
what is an oxidising agent
electron acceptor
144
give to features of a reaction at equilibrium
> rate of forward = rate of backwards
| > net. conc is the same
145
deduce what happens to the equilibrium when...
>the equilibrium will move to the (left/right)
> because the (forward/backwards) reaction is ...
>to oppose the change (of...)
146
What will happen to the equilibrium if the pressure is increased
move to the side with the fewest moles of gas
147
what will happen to the equilibrium if the temp is increased
it moves to the side that is endothermic
148
what will happen to the equilibrium if a catalyst is added
nothing
149
how do you work out half- equations
FEW-H~
150
what are the 3 stages of free radical substitution reactions
1] initiation
2] propagation
3] termination
151
Initiation
UV light causes homolytic fission and one elctron goes to each atom
152
what is a free radicals properties
very reactive
| high energy
153
propagation
Cl* + CH4 -> CH3* +HCL
or
CH3* + Cl2 -> CH3Cl + Cl*
> if you start with a * you end with an *
154
Termination
```
Cl* +Cl* -> Cl2
or
CH3* + Cl* ->CH3Cl
or
CH3* + CH3* -> CH3CH3
```
155
Ozone
O3
156
what does the Ozone exist in
a natural equilibrium with O2
157
Why are CFC's bad
they form Cl free radicals when exposed to UV in the upper atmosphere
> CFCl3 -> Cl* + CFCl2
these free radicals react with the Ozone
158
what are the two propagation steps in the CFC reaction with the ozone
1] O3 + Cl* -> ClO* + O2
2] ClO* + O3 -> 2O2 + Cl*
159
what is the overall reaction for the CFC reaction with the ozone
2O3 -> 3O2
160
what can we say the Cl* does to the ozone layer
catalyses the conversion of ozone into O2
161
primary alcohols
1 C bond
| O-H at the end
162
secondary alcohols
2 C bonds
| O-H at chain
163
tertiary alcohols
3 c bonds
| O-H at branch
164
primary alcohols are oxidised to...
aldehydes (CH2C=OH + H2O)
165
secondary alcohols are oxidised to...
ketones (CH3C=OCH3 + H2O)
166
an Aldehyde is oxidised to...
a carboxillic acid
167
what can we say about carboxillic acids and Ketones
they do not easily oxidise further because it would require a C-C bond to break rather than a H-C bond
