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.Chemistry - Nilay > AS Chemistry 2020 > Flashcards

AS Chemistry 2020 Flashcards

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1
Q

What is relative atomic mass

A

Mass of an atom compared to 1/12 of an atom of carbon-12

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2
Q

What is avogadro’s number

A

6.02x10^23

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3
Q

Volume of 1 mol of gas at r.t.p

A

24dm^3

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4
Q

What is mass spectrometer for

A

to determine masses of isotopes and their relative abundance

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5
Q

What is an orbital

A

A region of space where there is a high probability of finding an electron

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6
Q

What is Hund’s rule

A

Orbitals of the same energy remain singly occupied before pairing up

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7
Q

what are the 2 exceptions to the aufbau principle

A

Chromium: 4s1,3d5 NOT 4s2,3d4
Copper: 4s1,3d10 NOT 4s2,3d9

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8
Q

Define Ionisiation energy

A

Energy required to remove 1 mole of electrons from 1 mole of gaseous atoms to form 1 mole of gaseous cations.

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9
Q

Ionisation energy ______ across a period and ______ down a group

A

increases, decreases

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10
Q

Successive ionisation energies are always _____ than the previous one

A

greater

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11
Q

4 types of chemical bonds

A

ionic
covalent
dative covalent
metallic

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12
Q

3 types of physical bonds

A

Van der waals forces - weakest
dipole-dipole interaction
hydrogen bonds - strongest

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13
Q

Properties of giant ionic lattice:

A 
High M.P and B.P
Solid does not conduct
Liquid does conduct well
They are hard
The dissolve in water (to an extent) 
They are brittle
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14
Q

Properties of metals

A 
Conduct electricity
High M.P and B.P
Shiny
High density
Insoluble in most solvents
Malleable
Ductile
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15
Q

Definition of electronegativity

A

The attractive force of the nucleus of an atom on a shared electron pair in a covalent bond

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16
Q

Properties of non polar molecular solids

A 
Strong intramolecular forces
Weak intermolecular forces
Very low M.P and B.P
Do not conduct electricity
Soluble in non-polar solvents
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17
Q

What is polar covalent bonding

A

Bonds in which positive nuclei are both attracted to the negatively charged electron pair between them creating a permanent dipole.
Formed between atoms with high, but slightly different electronegativities.

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18
Q

Properties of polar molecular solids

A 
Strong intramolecular forces.
Strong intermolecular forces.
Low M.P and B.P
Do not conduct electricity
Soluble in polar solvents.
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19
Q

Properties of macromolecular solids

A

Very hard.
Do not conduct electricity
High M.P and B.P
Insoluble in all solvents.

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20
Q

What is a sigma bond

A

When electrons pair to occupy a single orbital that spreads over both atoms

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21
Q

What is a pi bond

A

electrons pair to occupy an orbital that has 2 lobes

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22
Q

Linear bond angle

A

180

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23
Q

trigonal planar bond angle

A

120

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24
Q

tetrahedral bond angle

A

109.5

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25
Q

trigonal pyramidal bond angle

A

107

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26
Q

V-shaped bond angle

A

105

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27
Q

Octahedral bond angle

A

90

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28
Q

trigonal bypyramid bond angle

A

90 and 120

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29
Q

3 conditions of the kinetic model of gases

A

particles moving in rapid and random motion;
particles are independant of eachother - no forces between them;
The volume occupied by the particles is negligible compared with the volume of the container.

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30
Q

What is Boyle’s law

A

At constant temp, for a given gas, volume is inversely proportional to pressure

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31
Q

What is Charles’ law

A

Volume of a given gas at constant pressure is proportional to its absolute temperature

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32
Q

What is the ideal gas law formula

A

PV = nRT

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33
Q

Definition of atomic radius

A

half of the average distance between the nuclei of 2 covalently or metal-bonded atoms

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34
Q

From top to bottom of a group, atomic radius _______

A

increases

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35
Q

From left to right of a period, atomic radius _______

A

decreases

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36
Q

3 Factors influencing first ionisation energy:

A

Size of the positive nuclear charge (larger size means stronger attractive force so higher I.E;

Distance of the electron from nucleus (further away electrons are easier to remove)

The shielding effect by electrons in the inner shells

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37
Q

Define organic compound

A

A compound consisting of carbon and any other elements

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38
Q

Define functional group

A

The site at which reactions take place in an organic molecule

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39
Q

Define homologous series

A

The family of compounds all having the same functional group and general formula

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40
Q

Define saturated compound

A

A compound with no double or triple bonds, incapable of undergoing addition reactions

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41
Q

Define catenation

A

The ability to form bonds between atoms of the same element

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42
Q

What are chain or branched chain isomers

A

Same number and type of atoms with different carbon skeletons

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43
Q

What are positional isomers

A

Molecules that have a substituent in different positions on the same carbon skeleton

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44
Q

What are functional group isomers

A

When molecules belong to different homologous series

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45
Q

What is sterioisomerism

A

Different spacial arrangement of atoms in a molecule

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46
Q

What is an addition reaction

A

When atoms are introduced to an unsaturated molecule

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47
Q

What is an elimination reaction

A

When new double or triple bonds are made between carbon atoms with the elimination of a small molecule such as hydrogen

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48
Q

What is a substitution reaction

A

When one atom is exchanged for another. There are 2 products formed

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49
Q

What is a condensation reaction

A

When two large molecules combine, discarding a small molecule, often H2O or HCl

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50
Q

What is a redox reaction

A

Reaction involving both oxidation and reduction half reactions

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51
Q

What is hydrolisis

A

Decomposition or alteration of a chemical substance by water

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52
Q

What is homolytic fission

A

The breaking of a covalent bond leaving both atoms in the bond with 1 electron each

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53
Q

What is initiation stage

A

The step producuing free radicals

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54
Q

What is propagation

A

Steps which produce products and more free radicals

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55
Q

What is termination

A

Steps where free radicals turn into molecules

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56
Q

4 Physical properties of alkanes

A

Non polar - do not mix with water
do not conduct electricity
M.P and B.P of branched chain alkanes lower than unbranched

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57
Q

2 chemical reactions of alkanes

A

Halogenation

Combustion

58
Q

Physical properties of alkenes

A

Non-polar

B.P increases with increased molar mass

59
Q

What is hydration

A

The addition of water to alkenes. Requires heat and dilute H2SO4 catalyst

60
Q

What is hydrogenation

A

The addition of hydrogento alkenes. Requires catalyst of platinum, nickel or palladium

61
Q

What is combustion

A

Alkenes burn in a smokier flame than the corresponding alkane to produce H2O, CO2, CO and some carbon

62
Q

What is used to oxidise alkenes, and what are the results in different conditions

A

Potassium permanganate.
In cold dilute solution, the alkene forms a diol.
In hot concentrated solution, the diol is split into fragments are further oxidised into ketones or carboxylic acid

63
Q

What is a catalytic converter and what is it’s catalyst.

A

Used in cars to remove pollutant gases from the exhaust using platinum/rhodium catalyst on a ceramic block.

64
Q

What is the balanced equation for the reduction of NO2 in a catalytic converter.

A

2NO + 2CO -> N2 + 2CO2

65
Q

What is oxidation number

A

Shows the relative state of oxidation or reduction of an element. Change in number means a redox reaction has occured.

66
Q

What is the trend in electronegativity going down group 17 and why

A

Decreases going down because atomic radius increases meaning there is less attraction to outer electrons and shared electrons.

67
Q

What is the trend in oxidising ability from top to bottom of group 17

A

Decreases from top to bottom, however all are strong oxidising agents - become reduced easily.

68
Q

What is the trend in vigour of reactions with hydrogen going down group 17

A

Decreases going down.

69
Q

Describe reaction of fluorine with hydrogen

A

explosive reaction as F-F bond is easy to break

70
Q

Describe reaction of chlorine with hydrogen

A

explosive reaction, only in the presence of sunlight

71
Q

Describe reaction of bromine with hydrogen

A

reacts only on heating with platinum catalyst

72
Q

Describe reaction of iodine with hydrogen

A

Very slow reaction, even on heating

73
Q

What is the trend in thermal stability of hydrogen halides going down group 17

A

Thermal stability decreases going down as H-Halogen bond energy decreases

74
Q

What is the appearance and solubility of hydrogen halides

A

all colourless gases and all very soluble in water

75
Q

When treated with a silver nitrate solution, what can be observed from Cl-,Br-,I-

A

Cl- ions form white ppt. soluble in dilute ammonia soln.
Br- ions form cream ppt. insoluble in dilute ammonia soln, but soluble in concentrated ammonia soln.
I- ions form a yellow ppt. insoluble in concentrated ammonia solution

76
Q

Are halogenoalkanes soluble in water? Why

A

No because they are non-polar

77
Q

As the molar mass of halogenoalkanes increases, solubility _______ and B.P ________

A

decreases, increases

78
Q

Why do branched chain result in lowered B.P?

A

The intermolecular forces are weaker between branched molecules.

79
Q

Why are alkyl flourides relatively unreactive

A

The C-F bond is strong

80
Q

What are the reagents and conditions in the formation of nitriles

A

Reagent: aqueous, alcoholic KCN or NaCN
Conditions: Reflux in aqueous alcoholic soln.

81
Q

What are the reagents and conditions for formation of primary amines

A

Reagent: alcoholic ammonia
Conditions: Reflux in alcoholic solution, pressure.

82
Q

What is the inductive effect?

A

When a halogen draws electrons towards itself

83
Q

Why do alcohols have relatively high B.P and M.P compared to alkanes?

A

Because of the presence of hydrogen bonds in their molecules. The -OH group makes part of the molecule polar.

84
Q

What products are formed by oxidising primary alcohols?

A

first to aldehydes, then further oxidised to carboxylic acids

85
Q

What products are formed by oxidising secondary alcohols?

A

Ketones

86
Q

What products are formed by oxidising tertiary alcohols?

A

Tertiary alcohols are not oxidised by common oxidising agents

87
Q

What is the Lucas test used for? What are the positive results?

A

To distinguish between water soluble alchohols.
Tertiary alcohols go cloudy immediately;
Secondary alcohols go cloudy in a few minutes.
Primary alcohols do not go cloudy until very long.

88
Q

How are alcohols dehydrated to alkenes? What catalyst is used?

A

By elimination of a water molecule using an acid catalyst

89
Q

How are esters formed from carboxylic acids? What catalyst is used?

A

By eliminating a water molecule using a concentrated H2SO4 catalyst

90
Q

What is the main difference between aldehydes and ketones?

A

Aldehydes have a single hydrogen atom bonded to the carbonyl atom while ketones always have two alkyl groups.

91
Q

6 Physical properties of carbonyl compounds

A

Colourless liquids at R.T.P
Higher M.P and B.P than alkanes of similar mass
Less volatile than corresponding alkanes
More volatile than corresponding alcohols
Cannot form hydrogen bonds
Aldehydes and Ketons with <5 carbon atoms are soluble in water.

92
Q

How are aldehyes formed.

A

By oxidation of primary alcohols then distillation.

93
Q

How are ketones formed.

A

By oxidation of secondary alcohols then distillation.

94
Q

2 Main differences in chemical reactivity of aldehydes vs ketones

A

Aldehydes are more reactive towards nucleophilic addition;

Aldehydes are more easily oxidised

95
Q

How are hydroxy nitriles produced

A

Addition of HCN to aldehydes/ketones

96
Q

What is produced by addition of hydrogen to aldehydes/ketones?

A

Aldehydes - first degree alcohols

Ketones - Second degree alcohols

97
Q

What is produced by reacting ketones/aldehydes with 2,4-DNPH?

A

Hydrazones

98
Q

What is observed when aldehydes react with Tollen’s reagent?

A

Silver mirror

99
Q

What is observed when ketones react with Tollen’s reagent?

A

No reaction

100
Q

What is observed when aldehydes react with Fehling’s solution or Benedict’s solution?

A

Red-brown ppt.

101
Q

What is observed when ketones react with Fehling’s solution or Benedict’s solution?

A

No reaction

102
Q

As size of carboxylic acids increases, B.P ________. Why?

A

increases due to increased van der waals forces

103
Q

What are the products of hydrolysis of esters? What catalyst must be used?

A

Products: Alcohol + Carboxylic acid
Catalyst: Any dilute acid or alkali

104
Q

Does exothermic reaction have positive or negative enthalpy change?

A

Negative

105
Q

Does endothermic reaction have positive or negative enthalpy change?

A

Positive

106
Q

What are the standard conditions of reaction

A

100kPa Pressure
25*C or 298K Temp
Concentration of 1mol/dm^3 for aqueous soln

107
Q

If energy released making bonds > energy used to break bonds is reaction endothermic or exothermic

A

Exothermic

108
Q

If energy released making bonds < energy used to break bonds is reaction endothermic or exothermic

A

Endothermic

109
Q

Equilibrium is reached when there is__________

A

No overall change (i.e. pressure and amount of reactants is constant)

110
Q

Why does the rate of reaction of a dynamic equilibrium decrease over time?

A

As the reaction proceeds the reactants get used up and the rate of reaction slows.

111
Q

What are 4 characteristics of a system in equilibrium

A
  • system is closed
  • no observable change in temp, pressure or ratio of reactants to products
  • Both reactants and products are present together
  • Both forward and reverse reactions are occuring at same rate.
112
Q

If concentration of reactants is increased in reaction which way will the equilibrium move?

A

Towards products

113
Q

If pressure is increased in an equilibrium which way will equilibrium shift?

A

Towards the larger number of gaseous molecules.

114
Q

If temperature of an equilibrium reaction is increased which way will equilibrium shift?

A

Exothermic: Towards reactants
Endothermic: Towards products

115
Q

Does a catalyst affect the position of an equilibrium?

A

No, only affects the speed at which the equilibrium is attained

116
Q

What are the reactants and conditions and catalyst for the Haber process?

A

3:1 Ratio of hydrogen:nitrogen gas.
Pressure: 350atm
Temp: 450*C
Catalyst: Iron

117
Q

Where are the reactants sourced for haber process?

A

Natural gas supplies hydrogen, nitrogen found in air.

118
Q

What is the contact process?

A

Industrial preparation of sulfuric acid,

119
Q

What are the 3 stages of contact process?

A

1) Sulfur is burned in air to make sulfur dioxide
2) The SO2 is further reacted with O2 over a vanadium pentoxide catalyst to make SO3
3) The SO3 is reacted with H2SO4 to from H2S2O7 (oleum) which then reacts with water to form sulfuric acid.

120
Q

An acid is a proton ____

A

donor

121
Q

What are 4 points of the collision theory

A
  • particles msut collide for a reaction take place
  • not all collisions lead to a reaction
  • reactants must possess a minimum amount of energy
  • particles must approach eachother with a certain orientation.
122
Q

What are group 2 metals known as

A

Alkaline earth metals

123
Q

The atomic radius of group 2 elements _____ from to to bottom

A

increases

124
Q

Why is the third ionisation energy of group 2 elements so much higher than 1st and 2nd?

A

They have to remove a valence shell which requires more energy

125
Q

Ionisation energy of group 2 metals ______ from top to bottom

A

decreases

126
Q

Group 2 metals become _____ reactive going down the group

A

more

127
Q

Flame colour of Mg

A

Bright white

128
Q

Flame colour of Ca

A

Brick red

129
Q

Flame colour of Sr

A

Red

130
Q

Flame colour of Ba

A

Green

131
Q

Group 2 nitrates become _____ thermally stable going down the group.

A

More

132
Q

Group 2 carbonates become ______ thermally stable going down the group

A

More

133
Q

Hydroxides of group 2 metals become _____ soluble going down the group

A

More

134
Q

Sulfates of group 2 metals become _____ soluble going down the group

A

Less

135
Q

Carbonates of group 2 metals become _____ soluble going down the group

A

Less

136
Q

Hydroxides of group 2 metals become _____ soluble going down the group

A

More

137
Q

What shape is the Ammonium ion

A

tetrahedral

138
Q

What is the oswald process

A

Production of nitric acid from ammonia

139
Q

What are the 3 stages of the oswald process

A

1) Ammonia is heated in air and passed over a heated catalyst of rhodium and platinum
2) Resulting mixture is cooled and more air is added.
3) More air is added and reactants are mixed with water

140
Q

What is eutrophication?

A

When nitrogen fertilisers enter waterways algae grows on surface of water blocking out light, so plants underwater die and oxygen is used up so water animals die

.Chemistry - Nilay (6 decks)

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