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.Chemistry - Nilay > A2 Chemistry 2021 > Flashcards

A2 Chemistry 2021 Flashcards

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1
Q

What is the bond angle in benzene

A

120

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2
Q

Why is benzene more stable than triene

A

Benzene has delocalised electrons in a pi system which are spread out, minimising repulsion.

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3
Q

What is the difference in energy required to react between benzene and triene called

A

Resonance energy

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4
Q

Reagents and conditions for nitration

A

Conc HNO3, Conc H2SO4, 50*C

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5
Q

What are uses of the products of nitration

A

Used to make TNT or dyes.

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6
Q

Reagents and conditions for Friedel-Crafts reaction

A

Acyl Chloride, AlCl3, Anhydrous

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7
Q

What is the electrophile in Friedel-crafts reaction

A

RCO+ (acylium ion)

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8
Q

Reagents and conditions for Halogenation

A

AlCl3 or FeCl3 catalyst, Anhydrous

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9
Q

Reagents and conditions for alkylation

A

AlCl3 or FeCl3 catalyst, Anhydrous

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10
Q

Why is phenol a weak acid

A

The electrons from the oxygen atom get delocalised into the pi system of the benzene ring, making the phenoxide ion more stable.

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11
Q

What is the difference between an aromatic alcohol and phenol

A

The oxygen atom in phenol is bonded directly to the benzene ring.

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12
Q

Reagents and conditions for diazotisation

A

Phenylamine, HNO2 or NaNO2, HCl, <10*C

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13
Q

4 stages to make phenol from benzene

A

1) Nitration
2) Reduction
3) Diazotisation
4) Substitution

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14
Q

What is formed when phenol reacts with sodium

A

Sodium Phenoxide ion, Hydrogen gas

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15
Q

Why does Br attach to the 2,4,6 positions on phenol

A

As the -OH group is electron releasing, it increases the electron density in the 2,4,6 positions

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16
Q

Reagents and conditions for nitration of phenol

A

Dilute HNO3, Room temp

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17
Q

How is acyl chloride formed

A

By adding PCl5, PCl3, SOCl2 to carboxylic acids.

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18
Q

What is formed when PCl5 reacts with carboxylic acids

A

POCl3 + HCl

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19
Q

What is formed when PCl3 reacts with carboxylic acids

A

H3PO4

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20
Q

What is formed when SOCl2 reacts with carboxylic acids

A

SO2 + HCl

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21
Q

Why do acyl chlorides have high B.p

A

C-Cl bond has permanent dipole due to polarity

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22
Q

Reagents and conditions for making amines from halogenoalkanes

A

Halogenoalkane + Hot, Ethanolic NH3

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23
Q

Why is Hot ethanolic NH3 used to make amines

A

To prevent the formation of 2* or 3* amines

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24
Q

Reagents and conditions for making amines from nitriles

A

Step 1: KCN/HCN in ethanol, heated under reflux with halogenoalkane

Step 2: Hydrogen with Ni catalyst, pass vapours over dry ether

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25
Q

What is observed when phenylamide is added to bromine water

A

Bromine water decolourises and a white precipitate is formed

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26
Q

Why are amines good bases

A

The nitrogen atom has a lone pair of electrons available to bond with a H+ ion

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27
Q

Why is ammonia not basic

A

The nitrogen atom does not have a lone pair of electrons available to bond with H+

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28
Q

Reagents for triiodomethane reaction

A

Aqueous alkaline Iodine, NaOH

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29
Q

Why must diazotisation be done at <10*C

A

The diazonium ion formed is very reactive

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30
Q

Which position does coupling usually occur in

A

4

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31
Q

What is reacted to form nitrous acid

A

NaNO2, HCl

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32
Q

When azo compounds are formed why do they always join in the 4 position

A

Phenol is a ring activating group

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33
Q

Why are amides pH neutral

A

The lone pair of electrons from the nitrogen are delocalised alongside the electrons from the oxygen, making the ability to attract H+ non-existent

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34
Q

What is reacted to form amides

A

Acyl chlorides with amines

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35
Q

What is formed when HCl is reacted with excess ammonia

A

NH4Cl

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36
Q

What is reacted with amides to form amines

A

LiAlH4

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37
Q

What is formed by the reaction of amides with acids

A
  • Carboxylic acids

- Ammonium or RNH3+ ions

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38
Q

What is formed by the reaction of amides with bases

A
  • Acid salts

- Amines/Ammonia

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39
Q

What is the bond between amino acids called

A

Peptide bond

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40
Q

What is reacted to form amino acids

A

Amine + Carboxylic acid

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41
Q

What is formed form the reaction between Amine + carboxylic acid

A

Amino acids

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42
Q

What is a zwitterion

A

Amino acid with H moved from O to N;

-ve charge on O, +ve charge on N

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43
Q

Do elements with higher E* value get oxidised or reduces more easily

A

Reduced

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44
Q

On which side of the cell does the more positive electrode go

A

Right side

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45
Q

How do you know if an electrolysis reaction is feasible

A

The emf value (RHS-LHS) is positive

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46
Q

At the positive electrode, which side of the half equation does the equilibrium sit

A

Left

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47
Q

What is the name for two combined half cells

A

Electrochemical cell

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48
Q

State the representation of the standard hydrogen electrode

A

Pt(s) | H2(g) | H+(aq)

49
Q

If there are no solid elements in a half cell, what is the electrode made of

A

Pt(s)

50
Q

What are the standard conditions

A

298K, 100kPa, 1M soln.

51
Q

On which side of the electrolysis reaction does the S.H.E sit

A

Left side

52
Q

What is the charge on 1 mole of e-

A

96500C

53
Q

How many coulombs in 1F

A

96500C

54
Q

What is a transition metal

A

A d-block element which forms one or more stable ions with incomplete d-orbitals.

55
Q

Why do 4s orbitals fill up before 3d orbitals.

A

Because they are lower in energy

56
Q

What are the 2 exceptions in the aufbau rule

A

Copper: [Ar]3d10,4s1
Chromium: [Ar]3d5,4s1

57
Q

Why are there 2 exceptions in the aufbau principle

A

More repulsion is caused by filling 4s sub shell.

Filling 3d sub shell provides more shielding to nucleus

58
Q

Which ‘transition metals’ are not actually considered transition metals

A

Scandium, Zinc

59
Q

What causes elements to have colour

A

Incomplete d-orbitals.

60
Q

What is an orbital

A

A region in which there is an extremely high probability of finding an electron

61
Q

Which d orbitals lie in between axis

A

dxy, dyz, dxz

62
Q

Which d orbitals lie on the axis

A

dx2-y2, dz2

63
Q

What is a ligand

A

A base with a lone pair of electrons which forms a dative bond with a central metal atom

64
Q

What is a bronstead acid/base

A

Proton donor/acceptor

65
Q

What is a lewis acid/base

A

Lone pair donor/acceptor

66
Q

What is a complex ion

A

A molecule or ion formed by a metal atom surrounded by 1 or more ligands

67
Q

Why are transition metals attractive to nucleophiles

A

They are relatively small and have a high charge density.

68
Q

What is meant by coordination number

A

The number of dative covalent bonds in a complex ion

69
Q

Why can complex sometimes only make 4 bonds

A

Due to steric hinderance eg Cl which is high charge density

70
Q

What is the coordination number of silver

A

2

71
Q

What are monodentate ligands

A

Ligand bonds to the metal with only 1 covalent bond.

72
Q

What are chelates

A

They bond to the metal ion in two different locations forming a ring

73
Q

What is the change in entropy when a chelate bonds to a complex ion

A

Increase

74
Q

What is the bond angle in a cis isomer of a complex ion

A

90 degrees

75
Q

If the bond angle in a complex ion is 180 degrees, what type of isomer is it

A

trans isomer

76
Q

What colour is a complex ion containing the OH- ligand

A

Pale blue

77
Q

What colour is a complex ion containing the H2O ligand

A

Deep blue

78
Q

What colour is a complex ion containing the Cl ligand

A

Green

79
Q

What colour is anhydrous CuSO4

A

White

80
Q

What is formed when the NH3 ligand is added to the copper complex ion

A

Blue ppt.

81
Q

What is a chelating agent

A

Ligands which form more than 1 dative bond

82
Q

If coordination number decreases, entropy _______

A

decreases

83
Q

If a complex ion solution is higher concentration, will it absorb more or less colour?

A

More

84
Q

What causes coloured compounds?

A

Ligands cause repulsion which causes orbitals to split. This allows electrons in partially filled d orbitals to absorb light energy and move between 2 non-degenerate orbitals and reflect light.

85
Q

What is a non-degenerate orbital

A

Orbitals which have been split due to the repulsion of ligands and consequently have different energy levels.

86
Q

When octahedral complex ions split, does the energy levels of the orbitals increase or decrease?

A

Increase

87
Q

When octahedral complex ions split, which orbitals are at a lower energy level

A

dxy, dyz, dxz

88
Q

What is the energy gap size between higher and lower energy level orbitals dependant on

A

Wavelength of light absorbed

89
Q

What is Kstab

A

The equilibrium constant for the overall reaction

90
Q

If Kstab of a reaction is more +ve, is it more or less stable?

A

More

91
Q

What is a polymer

A

A long chain molecule made from lots of small molecules joined together.

92
Q

What are the 2 types of polymerisation

A

Addition, Condensation

93
Q

What is reacted to form polyamides

A

Dicarboxylic acid + diamine

94
Q

What is formed from the polymerisation of amino acids

A

Polyamides

95
Q

What is reacted to form an ester

A

Carboxylic acid + alcohol

96
Q

What is reacted to form polyesters

A

Dicarboxylic acid + diol

97
Q

What is reacted to form an amide

A

Carboxylic acid + amine

98
Q

Why are condensation polymers generally more rigid than addition polymers?

A

Due to their polarity which creates H-bonds

99
Q

What is formed when a tertiary carbon is attacked by a photon

A

Free radical

100
Q

What is the double helix comprised of

A

2 sugar phosphate backbones linked by base pairs

101
Q

What are the 4 bases in DNA

A

cytosine
thymine
adenine
guanine

102
Q

Where do the bases attach to the sugar backbones

A

In place of the -OH on the 1-carbon

103
Q

How is nucleotide formed

A

Attaching a base to the sugar backbone

104
Q

Outline the DNA replication process

A

Effectively, the double helix is split between the base pairs, and new bases attach to these split ones.

105
Q

What are proteins comprised of

A

Amino acids joined together by peptide bonds.

106
Q

What is meant by the primary structure of proteins

A

Describes the order of amino acids used to make up the protein

107
Q

What is meant by the secondary structure of proteins

A

Alpha helixes and beta pleated sheets

108
Q

How and where are secondary structures held together

A

H-bonds between lone pair on O and H attached to N atom

109
Q

What is the shaped of an alpha helix

A

Protein chain in a loose coil

110
Q

What is the shape of a beta pleated sheet

A

Protein chains folded alongside eachother

111
Q

What is meant by the tertiary structure of proteins

A

Describes the way the whole chain (incl. secondary structure) is arranged in it’s final 3D shape

112
Q

What types of interactions hold the tertiary structure together

A
  • Ionic interactions
  • Hydrogen bonds
  • van der waals forces
113
Q

Why does PTFE have a relatively high M.P despite weaker van der waals forces

A

Because the molecules are essentially straight, they can like very close together, therefore the intermolecular forces are still strong.

114
Q

Why is kevlar extremely strong material

A

The polymers are arranged in sheets, which allows for strong H-bonds between strands of kevlar.

115
Q

What are the 3 types of adhesive polymers

A

Silicon containing resins
Epoxy resins
Super glues

116
Q

What makes silicon containing resins strong adhesives

A

The Si-O-R groups are hydrolysed, causing cross linking between polymers.

117
Q

What makes epoxy resins adhesive

A

A curing agent such as a diamine is used to crosslink epoxy groups to form large polymers.

118
Q

What makes super glues adhesive

A

The cyanoacrylate is very polar and is nucleophilic attacked by water molecules, forming large polymer chains.

119
Q

What makes polymers conductive

A

pi bonds overlap p-orbitals which means there is a high potential for delocalised electrons.

.Chemistry - Nilay (6 decks)

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