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AS Level Chemistry > chem > Flashcards

chem Flashcards

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

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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

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3
Q

what are the chemical formulae of phosphorus, sulphur and chlorine

A

P4
S8
CL2

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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.

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5
Q

what type of structure does phosphorus, sulphur and chlorine have

A

molecular

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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

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7
Q

why are 2nd ionisation energies greater than 1st ionisation energies?

A

takes more energy to remove an electron from a positive ion

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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

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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

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10
Q

write an equation for the first ionisation energy of E

A

E(g) -> E+(g) + e-

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11
Q

what type of structure does silicone have

A

macromolecular

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12
Q

why does temp not increase while a substance is melting or boiling

A

the energy is absorbed as the bond weakens

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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

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14
Q

starting with the weakest, name the 3 types of intermolecular attraction

A

van der waals
permanent dipole-dipole
hydrogen bonding

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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

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16
Q

what are giant covalent bond held together by

A

covalent bonds

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17
Q

what can we say about the polarity of bonds in elements

A

they are not polar

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18
Q

what are molecular crystals held together by

A

intermolecular force hold molecules together covalent bonds hold the atoms within molecules together

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19
Q

what is a dative covalent bond

A

a shared pair of electrons, where both have been supplied by one atom

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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

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21
Q

what causes permanent dipole-dipole forces

A

attraction between molecules with permanent dipoles

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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

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23
Q

what are ionic crystals held together by

A

electrostatic attraction between oppositely charged particles

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24
Q

what are the four types of crystal structures

A

ionic, metallic giant covalent and covalent

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25
Q

where do we find van der waals and what effects its strength

A

found in all atoms and molecules. the more molecules the bigger the force

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26
Q

how do we convert cm3 to dm3

A

divide by 1000

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27
Q

if we make a change to conc. temp. or pressure how will the equilibrium respond

A

it will move to reduce the disturbance

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28
Q

why might a compromised temp be used

A

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

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29
Q

other than yield why might a compromise pressure be used

A

cheaper

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30
Q

why do haber process plants run at a higher temp and lower pressure that would produce the maximum conversion

A

high temp = faster

low pressure = less expensive

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31
Q

ammonia

A

NH3

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32
Q

what is 80% of ammonia used to make

A

fertilisers

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33
Q

define molecular mass

A

the average mass of a molecule compared to 1/12th the mass of an atom od C-12

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34
Q

what equation links moles, conc, and volume

A

n=cxv/1000

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35
Q

define relative atomic mass

A

the average mass of an atom compared to 1/12th of the mass of C-12

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36
Q

what effect does a catalyst have on the position of equilibrium

A

none

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37
Q

write an ionic equation to summarise NaOH+HCL -> NaCL=H2O

A

H+(aq) + OH-(aq) -> H2O (l)

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38
Q

what is the difference between dynamic equilibrium and equilibrium

A

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

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39
Q

what is methanol used for

A

motor fuel

starting material

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40
Q

what is ethanol made from ethane used for

A

making cosmetics, drugs, inks, detergent

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41
Q

give the chemical reaction for the hydration of ethane to form ethanol

A

C2h4 + h2o -> c2h5oh

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42
Q

what is the equation for calculating % yield

A

(actual yield/ theoretical) x100

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43
Q

how do you convert from empirical formula to molecular formula

A

work out mass of the empirical and molecular formula. divide empirical by molecular. multiply the number by each element in the empirical formula

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44
Q

what is an equilibrium mixture

A

the mixture of chemicals found in a dynamic equlibrium

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45
Q

what is the equation used to calculate % economy

A

molecular mass of desired product/sum of all molecular masses x100

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46
Q

what is empirical formula

A

the simplest ratio of atoms of each elements in a compound

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47
Q

what is a reversible reaction

A

a reaction which can proceed in either direction between reactants and products

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48
Q

in the context of heterogeneous and homogeneous what is a phase

A

different physical state

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49
Q

what are the two catalysts what do they mean

A

homogeneous- same phase

heterogeneous- different phase

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50
Q

how do catalyst work

A

they provide an alternative route for the reaction, with a lower activation energy

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51
Q

what effect do catalysts have on the position of equilibrium for reversible reactions

A

none

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52
Q

what is the meaning of the term catalyst

A

something that alters the rate of a chemical reaction, but is not used up in the reaction

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53
Q

what does increasing the conc. increase the rate of reaction

A

makes collisions more likely

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54
Q

why does temp have such a big impact on rate

A

temp increases the number of particles with energy above the activation energy

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55
Q

on a M-B distributions, where is the average energy in reletion to the most probable

A

right

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56
Q

do most collisions between particles result in a chemical reaction why

A

no

they may not have enough energy or the wrong orientation

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57
Q

five factors that effect rate reaction

A 
temp
conc
pressure
surface area
catalyst
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58
Q

what is the catalyst in a catalytic converter in a honeycomb shape

A

to provide a much greater surface area

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59
Q

define activation energy

A

minimum amount of energy to start a reaction and break bonds

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60
Q

do any particles in a gas have 0 energy

A

no

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61
Q

what are zeolites

A

minerals with a very open pore structures that ions or molecules can fit into. they are used as catalysts

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62
Q

what does collision theory tell us

A

that reactions can only occur when collisions take place between particles that have enough energy

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63
Q

what effect to catalyst have on enthalpy change for reactions

A

none

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64
Q

what does the prefix ‘di’ mean

A

two of them

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65
Q

what does the production of greenhouse gases contribute towards

A

global warming

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66
Q

why do we crack hydrocarbons

A

to produce smaller molecules that are higher in demand

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67
Q

what is empirical formula

A

the simplest whole number ratio in which atoms in a compound combine together

68
Q

what greenhouse gas, does burning fossil fuels release into the atomosphere

A

CO2

69
Q

what does a negative sigh infront of delta H mean

A

forward reaction is exothermic

70
Q

name a catalyst used in a catalytic converter

A

platinum or rhodium

71
Q

give the equation for the reaction of carbon monoxide with hydrogen to form methanol

A

CO + 2H2 -> CH3OH

72
Q

how do you convert concs. from gdm-3 to moldm-3

A

divide by molar mass

73
Q

what is meant by agravados constant

A

number of partials in a mole.

74
Q

how does fractional distillation work

A

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
Q

what are the 1st six prefixes of organic molecules

A 
meth
eth
prop
but
pent
hex
76
Q

where do we collect shorter chain hydrocarbons from in a fractionating tower

A

near the top

77
Q

where we have more than one functional group, how do we decide which one to write first

A

functional groups go in alphabetical order

78
Q

what does cracking do to the c-c bonds in alkanes

A

breaks them

79
Q

what do we call a hydrocarbon with a =

A

alkene

80
Q

when writing out names of molecules, where do we put a hyphen

A

between names and numbers

81
Q

what problems might carbon produced by incomplete combustion have on health and the environment

A

asthma, damages lungs and global diming

82
Q

what do we call the thick residue that collects at the bottom of the fractioning tower

A

tar/ bitumen

83
Q

what is meant by displayed formula

A

a formula of a compound drawn out so that every carbon atom and every bond is shown

84
Q

what homologous series is petroleum mainly made of

A

alkanes

85
Q

what are the conditions and main products of thermal cracking

A

high temp
high pressure

high percentage of alkenes

86
Q

what issues are there with burning a fuel that contains sulfur

A

sulphur dioxide will be produced that causes acid rain

87
Q

what amount of energy do most particles have? how can we find this from a M-D distribution

A

an intermediate amount of energy at the peak of the curve

88
Q

what are functional group isomers

A

where isomers have different functional groups

89
Q

what are the 3 types of structural isomers

A

chain, position, functional group

90
Q

what are positional isomers

A

where the functional group in isomers is attached to the main chain at different points

91
Q

how is sulphur dioxide removed from flue gases

A

using CaO

this reacts with the SO2 to produce CaSO4 which is used as plaster

92
Q

where must a reaction be in order for a dynamic equilibrium to be reached

A

a closed system

93
Q

what can we say about the proportion of reactants and products at equilibrium

A

any ratio not 50;50

94
Q

how do we remove the pollutants produced by the internal combustion engine

A

using a catalytic converter

95
Q

when moving left to right across period 3, what exceptions are there for the trend in increasing 1st ionisation energy? why?

A

aluminium- electron removed by 3p

sulphur- two electrons in 3p so repulsion occurs

96
Q

what are alkanes

A

saturated hydrocarbons

97
Q

what two products are produced by the complete combustion of hydrocarbons

A

carbon dioxide and water

98
Q

what is meant by molar volume

A

1 mole of any gas takes up 24000 of space at room temp and pressure

99
Q

what is meant by homologous series

A

a set of organic compounds with the same functional group

100
Q

what is meant by functional group

A

an atom or group of atoms in an organic molecule which is responsible for the characteristic reactions of that molecule

101
Q

what is meant by structural formula

A

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
Q

what is structural isomerism

A

where molecules have the same molecular formula, but a different structural formula

103
Q

what are the conditions and main products of catalytic cracking

A

slight pressure
high temp
zeolite catalyst

104
Q

what are chain isomers

A

where the hydrocarbon chain in isomers is arranged differently

105
Q

what products would we expect from the incomplete combustion of a hydrocarbon

A

carbon monoxide and water

106
Q

what is le chateliers principle

A

if a system in equilibrium is disturbed, the equilibrium moves in the direction that tends to reduce the disturbance

107
Q

in practice what conditions are used for producing methanol from carbon dioxide and hydrogen

A

500K

10,000kPa

108
Q

what is the equation for the Haber process

A

N2 + 3H2 2NH3

109
Q

what temp and pressure is used in most plants for the haber process

A

20,000kPa

670K

110
Q

what do we call the process of reactants sticking to the surface of a catalyst

A

adsorption

111
Q

which catalyst is used in the production of ethanol from ethene

A

phosphoric acid absorbed on silica

112
Q

in practice, what conditions are used to produce ethanol from ethene

A

570K

6500kPa

113
Q

what do we call the process of breaking away from the surface of a catalyst

A

desorption

114
Q

what type of structure does argon have

A

atomic

115
Q

what happens to the total area under a M-B distribution curve when the temp is changed

A

no change

116
Q

what causes Van Der Waals forces

A

caused by instantaneous dipoles. these occur because in any instant electrons are not spread evenly and more will be in one another.

117
Q

what do we call a hydrocarbon with a group 7 element attatched

A

halo- alkane

118
Q

what can we say about a reaction in dynamic equilibrium

A

in a closed system, the rate of the forward and reverse reactions are the same so conc. is same

119
Q

what are alkanes mainly used for

A

fuels

120
Q

what happens to the boiling point of alkanes as chain length increases

A

increases

121
Q

name 3 greenhouse gases

A

CO2
methane
water vapour

122
Q

in terms of electrons, what is oxidation and reduction

A

Oxidation is loss of electrons

Reduction is gain of electrons

123
Q

what does an oxidising agent do in terms of electrons

A

accept electrons

124
Q

what does a reducing agent do in terms of electrons

A

donate electrons

125
Q

what is the oxidation state of hydrogen

A

+1 except in metal hydrides where it is -1

126
Q

what is the oxidation state of Group 1

A

always +1

127
Q

what is the oxidation state of Group 2

A

always +2

128
Q

what is the oxidation state of Group 3

A

always +3

129
Q

In the thermite reaction Fe2O3 + Al -> Fe + AlsO3. what is oxidised and what is reduced

A

Fe is reduced from +3 to 0

Al is oxidised from 0 to +3

130
Q

what are the 3 nucleophiles used in nucleophilic substitution reaction

A

Hydroxide
Cyanide
Ammonia

131
Q

why is excess ammonia used in nucleophillic substitution reaction

A

to reduce the chance of the amine taking part in further substitution reactions

132
Q

what are elimination reactions

A

when haloalkanes can react with hydroxide ions in an alternative mechanism. instead of producing an alcohol we produce an alkene

133
Q

what happens if you react sodium/potassium hydroxide with a haloalkane

A

both nucleophillic substitution and elimination reactions.

134
Q

how do you favor an elimination reaction

A

> concentrated NaOH/KOH
ethanol as solvent
high temp

135
Q

how do you favor nucleophillic substitution reaction

A

> more dilute NaOH/ KOH
water as solvent
Low temp

136
Q

what do the hydroxide ions act as in elimination reactions

A

a base

137
Q

what do the hydroxide ions act as in nucleophillic substitution reactions

A

a nucleophile

138
Q

what is critical for E/Z isomerism to exist

A

A must not = B and C must not = D

139
Q

E isomerism

A

> trans

> opposite look like a Z

140
Q

Z isomerism

A

> cis

> next to look like a E

141
Q

what do electrophillic addition reactions happen with

A

> Halides eg HBr and HI
Bromine
H2SO4

142
Q

what is a reducing agent

A

electron donor

143
Q

what is an oxidising agent

A

electron acceptor

144
Q

give to features of a reaction at equilibrium

A

> rate of forward = rate of backwards

> net. conc is the same

145
Q

deduce what happens to the equilibrium when…

A

> the equilibrium will move to the (left/right)
because the (forward/backwards) reaction is …
to oppose the change (of…)

146
Q

What will happen to the equilibrium if the pressure is increased

A

move to the side with the fewest moles of gas

147
Q

what will happen to the equilibrium if the temp is increased

A

it moves to the side that is endothermic

148
Q

what will happen to the equilibrium if a catalyst is added

A

nothing

149
Q

how do you work out half- equations

A

FEW-H~

150
Q

what are the 3 stages of free radical substitution reactions

A

1] initiation
2] propagation
3] termination

151
Q

Initiation

A

UV light causes homolytic fission and one elctron goes to each atom

152
Q

what is a free radicals properties

A

very reactive

high energy

153
Q

propagation

A

Cl* + CH4 -> CH3* +HCL
or
CH3* + Cl2 -> CH3Cl + Cl*
> if you start with a * you end with an *

154
Q

Termination

A 
Cl* +Cl* -> Cl2
or
CH3* + Cl* ->CH3Cl
or
CH3* + CH3* -> CH3CH3
155
Q

Ozone

A

O3

156
Q

what does the Ozone exist in

A

a natural equilibrium with O2

157
Q

Why are CFC’s bad

A

they form Cl free radicals when exposed to UV in the upper atmosphere
> CFCl3 -> Cl* + CFCl2
these free radicals react with the Ozone

158
Q

what are the two propagation steps in the CFC reaction with the ozone

A

1] O3 + Cl* -> ClO* + O2

2] ClO* + O3 -> 2O2 + Cl*

159
Q

what is the overall reaction for the CFC reaction with the ozone

A

2O3 -> 3O2

160
Q

what can we say the Cl* does to the ozone layer

A

catalyses the conversion of ozone into O2

161
Q

primary alcohols

A

1 C bond

O-H at the end

162
Q

secondary alcohols

A

2 C bonds

O-H at chain

163
Q

tertiary alcohols

A

3 c bonds

O-H at branch

164
Q

primary alcohols are oxidised to…

A

aldehydes (CH2C=OH + H2O)

165
Q

secondary alcohols are oxidised to…

A

ketones (CH3C=OCH3 + H2O)

166
Q

an Aldehyde is oxidised to…

A

a carboxillic acid

167
Q

what can we say about carboxillic acids and Ketones

A

they do not easily oxidise further because it would require a C-C bond to break rather than a H-C bond

AS Level Chemistry (7 decks)

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