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Extra Chemistry Stuff > Paper 2 Questions > Flashcards

Paper 2 Questions Flashcards

1
Q

The main greenhouse gases and their effect

A

H2O vapour, CO2 and methane
They absorb IR radiation which makes the molecules vibrate more which gets passed onto neighbouring molecules. This extra kinetic energy raises the overall temperature

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2
Q

What is Markownikoff’s rule?

A

The major product from addition of a hydrogen halide to an unsymmetrical alkene is the one where hydrogen adds to the carbon with the most hydrogen already attached.

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3
Q

Acyl Chloride and Phenol…

A

Ester and HCl

slow reaction

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4
Q

Explain the polarity of an alcohol

A

Polar bond between C-O bond where the hydroxy group pulls electrons away from the carbon. Also polar bond between O-H as oxygen pulls electrons away from the hydrogen

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5
Q

What is the evidence against the Kekulé model?

A

The enthalpy change of hydrogenation on the double bond of cyclohexene is -120jkmol. If benzene had three double bonds, it would have an enthalpy change of -360jkmol but it’s actually -208jkmol, so it can contain 3 double bonds.

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6
Q

Explanation of boiling points of alkanes

A

Longer chains have more London forces due to a larger surface area so there is more surface contact between molecules. Therefore longer chains have higher boiling points.

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7
Q

How are polyesters formed?

A

The carboxyl group (OH from COOH) react with the hydroxyl group (H from OH) the to form ester links. A water molecule is lost each time.

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8
Q

Test for Carboxylic acid

A

Add solid carbonate, if the solution fizzes, bubble the gas through lime water which will turn cloudy

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9
Q

Shape and angle around C=C double bonds

A

Trigonal planar, 120°

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10
Q

3 types of structural isomers

A
  1. Chain isomers: e.g. carbon chain can be straight or branched
  2. Position isomers: functional group is attached to a different carbon
  3. Functional group isomers: e.g. Hexene is an isomer of cyclohexane, they have different functional groups but the same molecular formula
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11
Q

Are double bonds nucleophilic or electrophilic?

A

Nucleophilic

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12
Q

Test for primary/secondary alcohols

A

Add drops of unknown solution to acidified dichromate and warm in a water bath. The solution is primary or secondary alcohol, solution will turn from orange to green.

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13
Q

Examples of nucleophiles

A

CN-
NH3
OH-

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14
Q

How does a mass spectrometer work?

A

Molecules in the sample are bombarded with electrons and a molecular ion, M+, is formed when the bombarding electrons remove an electron from the molecule.

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15
Q

Explain why halogen carriers are needed for benzene to react with Br2

A

Without the halogen, the electrophiles doesn’t have a strong enough positive charge to attack the stable benzene ring.

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16
Q

Carboxylic Acid and Carbonates form…

A

Salt, CO2 and H2O

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17
Q

What is a radical?

A

Particles with an unpaired electron, they are very reactive

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18
Q

Which groups are electron withdrawing? (3,5 directing)

A

-NO2

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19
Q

Reaction mechanism and condition for synthesis of chloromethane (initiation)

A 
Cl2 -> Cl•
UV light (photochemical reaction)
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20
Q

Equation for Rf value

A

Rf = distance travelled by spot/distance traveled by solvent

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21
Q

Why are Friedel-Crafts reactions important to synthesis?

A

It results in the formation of a new C-C bond, which are difficult to make.

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22
Q

How to distinguish between an aldehyde and a ketone

A

Add Tollens reagent (silver nitrate dissolved in aqueous ammonia) and heat. Aldehydes will form a silver mirror and ketones won’t.

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23
Q

Carboxylic Acid + Alcohol…

And name the catalyst

A

Ester and H2O

Strong acid catalyst

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24
Q

Why is a C=C double bond planar?

A

The electron pairs will try to repel each other as much as possible

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25
Q

2 methods of hydrolysing haloalkanes to form alcohols

A
  1. Hydrolysis with aqueous alkali
    RX + OH- -> ROH + X-
  2. Hydrolysis with water
    RX + H2O -> ROH + H+ + X-
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26
Q

How to name an Ester

A
  1. The alkyl group attached to the single bond oxygen is the first part of the name e.g. ethyl
  2. The alkyl group attached to the C=O is the second part of the name e.g. methanoate
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27
Q

What link is formed by polyesters and polyamides?

A

Polyester: -COO-
Polyamides: -CONH-

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28
Q

When using gas chromatography, how do you work out the percentage of a substance in the original mixture?

A

% in original mixture = area of peak/total area of all peaks

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29
Q

Advantages of renewable raw material

A
  • Won’t run out like oil
  • If it is plant based, the CO2 released is just the same CO2 that the plant has absorbed, so it won’t form anymore CO2
  • Plant polymers can save energy compared to oil based plastics
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30
Q

Dicarboxylic Acid + Diamine …

A

Polyamide

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31
Q

Psychical properties of alcohols

A

Low volatility
High boiling point (hydrogen bonding)
Mainly soluble

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32
Q

Acyl Chloride and H2O forms…

A

Carboxylic Acid and HCl

vigorous reaction

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33
Q

Give examples of halogen carriers

A

AlCl3, FeCl3

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34
Q

What does the delocalised model of benzene show?

A

The p-orbitals of all six carbon atoms overlap to create a pi-system made up of two ring-shaped clouds of electrons.
All the C-C bonds in the ring are the same length.
The electrons in the ring are said to be delocalised.

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35
Q

What is IR spectroscopy used for?

A
  • Breathalysers (C-H bonds)

- Monitoring pollutants (N=O, C triple bond O)

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36
Q

What are Acid anhydrides made of?

A

Two Carboxylic Acid molecules joined together via an oxygen. Forms waters

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37
Q

Definition of displayed formula

A

Shows how all the atoms are arranged and all the bonds between them

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38
Q

Definition of structural formula

A

Shows the atoms carbon by carbon with attached hydrogen and functional groups

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39
Q

Explain the role of AlCl3 in acylation

A

It accepts a lone pair of electrons from the Acyl Chloride which increases its polarity forming a carbocation which gives it a strong enough charge to react with the benzene ring

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40
Q

Why are electrophiles attracted to aromatic compounds?

A

The benzene ring is an area of high electron density. Electrophiles are usually electron deficient.

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41
Q

What toxis gas is formed when burning PVC and how is it removed?

A

HCl, passed through a scrubber so it can react with a base to neutralise the gas

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42
Q

Why do alkenes form stereoisomers?

A

Because there is restricted rotation around the C=C bond, this is caused by the p-orbitals having to stay in the same position to overlap and form a pi-bond

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43
Q

What is the orbital overlap model?

A

It states that covalent bonds can form between two atoms if they’re arranged so that the outer atomic orbitals overlap. The orbitals combine to form a shared orbital that forms a bond between the atoms. How well the orbitals overlap determines how strong the bond is. This type of covalent bond is called a sigma bond.

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44
Q

Ways in which plastic can be recycled

A

Cracking or remoulding

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45
Q

What is the standard substance used in NMR to compare against

A

(TMS) tetramethylsilane which will produce a peak at delta=0 which you can ignore

46
Q

Reaction mechanism for synthesis of chloromethane (propagation)

A

Cl• + CH4 -> CH3• + HCl

CH3• + Cl2 -> CH3Cl + Cl•

47
Q

What is the difference between a sigma and pi bond?

A

Sigma is a single covalent bond. Pi bonds occur when two p-orbitals overlap sideways, one above and one below the molecular axis.

48
Q

Haloalkane and ethanolic ammonia (excess)…

A

Amine and NH4+BR-

49
Q

How to identify a monomer that form a condensation polymer:

A
  • remove the bond in the middle of the amide/ester link (either between C-N or C-O)
  • add OH groups onto the C=O group to form a carboxyl group
  • for polyamides, add hydrogens onto the NH group to form NH2
  • for polyesters, add hydrogens onto the oxygen to form OH group and add OH groups onto any terminal carbon atoms
50
Q

Explain the reaction of phenol with bromine water

A

It will undergo electrophilic substitution. One of the lone pairs of electrons in a p-orbital if the oxygen atoms overlaps with the delocalised ring of electrons. This increases the electron density of the ring, making it more likely to be attacked by electrophiles.

51
Q

Explain the basicity of amines

A

In amines, the lone pair of electrons on the nitrogen can form a dative covalent bond with a H+ ion to form NH4+

52
Q

What do curly arrows show?

A

The movement of an electron pair/how covalent bonds are broken

53
Q

Carboxylic Acid and Metal Oxide/Hydroxide form…

A

Salt and H2O

54
Q

What is a chiral carbon?

A

A carbon with 4 different groups attached to it

55
Q

General formula for an alpha-amino acid

A

RCH(NH2)COOH

56
Q

How to plot a callibration curve

A
  1. Create a series of standard solutions of different concentrations of the analyte, the substance that you are detecting
  2. One by one, injection standard solutions into gas chromatography instrument, record results
  3. For each chromatogram, calculate area under the peak that corresponds to the analyte
  4. Plot these area values on a graph of area vs concentration and draw a line of best fit
57
Q

Reactivity of alkanes

A

Pretty reactive because C=C bonds have a really high electron density and because the pi-bond sticks out from the molecule so it is more likely to be attacked by electrophiles.

58
Q

Which will have a lower boiling point, a straight chain alkane or a branched chain alkane?

A

Branched chain alkane, because they can’t pay closely together so induced dipole-dipole interactions are reduced

59
Q

Factors that affect retention time

A
  • solubility of substance (lower solubility means lower retention time)
  • boiling point (lower boiling point means lower retention time)
  • temperature (higher temperature means lower retention time)
60
Q

Heterolytic fission explanation

A

Bond breaks unevenly with one bonded atom receiving both electrons. This forms a cation and an anion
XY -> X+ + Y-

61
Q

Examples of electrophiles

A

NO2+

H+

62
Q

What is cis-trans isomerism

A

E/Z isomerism where each carbon has at least one group in common.

63
Q

Properties of CFCs

A

Volatile
Non toxic
Non flammable
Not very reactive

64
Q

Which functional groups have an electron deficient functional group?

A

Nitrile, Carboxylic Acid, Ester, Acyl Chloride, Acid anhydride

65
Q

Homolytic fission

A

Bond breaks evenly so each bonding atom receives one electron from a bonded pair. This forms two electrically uncharged radicals.
XY -> X• + Y•

66
Q

How to CFC’s caused breaking down of the ozone layer

A

CFC splits into two radicals including a chlorine radical.
CF2Cl2 -> CF2Cl• + Cl•
They attack the ozone molecule
O3 + Cl• -> O2 + ClO•
ClO• + O -> O2 + Cl•
The Cl• radical is regenerated because it is a catalyst so it can keep destroying ozone molecules
Overall: O3 + O -> 2O2

67
Q

Reaction mechanism for synthesis of chloromethane (termination)

A

CH3• + Cl• -> CH3Cl
CH3• + CH3• -> C2H6
Cl• + Cl• -> Cl2

68
Q

The 5 step guide to nomenclature

A
  1. Count the longest carbon chain
  2. Add the prefix or suffix of the functional groups
  3. Assign the function group onto the lowest number possible
  4. Add side chains or lesser functional groups at the start, in alphabetical order
  5. Use di, tri and tetra for multiples of functional groups or side chains, do not include in the alphabetical order
69
Q

Which groups are electron donating? (2,4,6 directing)

A

-OH or -NH2

70
Q

Functional group of Acyl Chlorides

A

COCl

71
Q

Which functional groups have a polar C=O bond

A

Aldehydes and ketones

72
Q

Definition of skeletal formula

A

Shows the bonds of the carbon skeleton only, and any functional group

73
Q

Carboxylic Acid and Metal forms…

A

Salt and Hydrogen

74
Q

How does NMR work?

A

A sample of a compound is placed in a strong magnetic field and exposed to range of different frequencies of low-energy radio waves. The nuclei of certain atoms absorb energy from the radio waves and will depend on the environment that it’s in.

75
Q

What is bond fission?

A

Breaking of a covalent bond

76
Q

Factors affecting Rf values

A
  • The adsorption of the substance

- The coating on the plate e.g. silica gel or aluminium powder

77
Q

What types of bonds is a double bond made up of

A

Sigma and pi

78
Q

Acyl Chloride and Primary Amine…

A

Secondary Amide and HCl

violent reaction

79
Q

Acyl Chloride and Alcohol forms…

A

Ester and HCl

vigorous reaction

80
Q

General equation for a reaction between a Haloalkane and cyanide reagent (e.g. KCN, NaCN or HCN)

A

RX +CN⁻ -> RCN + X⁻

81
Q

What are condensation polymers?

A

Where two different types of monomer, each with at least two functional groups, react to form a link, creating a polymer chain. E.g. polyesters and polyamides

82
Q

How are polyamides formed?

A

The carboxyl group (OH from COOH) react with the amino group (H from NH2) the to form amide links. A water molecule is lost each time.

83
Q

What is the test for carbonyls?

A

Add 2,4-DNPH dissolved in methanol and H2SO4. Forms bright orange precipitate if a carbonyl group is present. Precipitate can then be recrystallised and used to determine melting and boiling point by comparing it against a database of known values.

84
Q

Explanation of reactivity of alkanes

A

Fairly unreactive but will combust in oxygen and undergo substitution with highly reactive free radical species.
The C-C or C-H sigma bonds have a large bond enthalpy, making them very strong and difficult to break. They are also non-polar so won’t attract any negatively or positively charged particles.

85
Q

Amide functional group

A

CONH2

86
Q

Acyl Chloride and NH3…

A

Primary Amide and HCl

violent reaction

87
Q

Shape and angle of bonding around saturated carbon atoms

A

Tetrahedral, 109.5°

88
Q

Problems with radical substitution

A
  • You will get multiple unwanted products formed. E.g. production of chloromethane will result in dichloromethane, trichloroethane and tetrachloromethane. You can over come this by having an excess of methane.
  • A mixture of isomers will be formed as substitution can happen anywhere along the carbon chain.
89
Q

Explain why solubility decreases with size in alcohols

A

Partial positive charge caused by polar bonds on the hydrogen can attract lone pairs on an oxygen from a water molecule forming hydrogen bonds. In larger alcohols, most of the molecule is non-polar so there’s less attraction to water.

90
Q

What does dehydrating an alcohol form?

A

An alkene

91
Q

Dicarboxylic Acid + Diol…

A

Polyester

92
Q

How could a polymer be formed with both an amide and an ester link?

A

From a molecule that contains an amine and an alcohol group, and a carboxylic acid
or
From a molecule that contains a carboxylic acid group and either and alcohol or an amine group (self polymerisation)

93
Q

Explain why a mixture of primary, secondary, tertiary and quaternary amines can be produced

A

Because more than one hydrogen is likely to be produced. As long as nitrogen has a long pair of electrons, it can go on to react again.

94
Q

What is IR spectroscopy?

A

When a beam of IR radiation is passed through a sample of a chemical. It is absorbed by the covalent bonds in the molecules, increasing their vibrations

95
Q

Acid hydrolysis of an Ester involves…

A

Splitting the Ester into a Carboxylic acid and an alcohol under reflux

96
Q

Definition of homologous series

A

A family of compounds that have the same functional group and general formula

97
Q

Other radical that can can catalyse the breakdown of the atmosphere and where it come from

A

NO•

Produced by car and aircraft engines, and thunderstorms

98
Q

Things to remember when reading a mass spectrum:

A
  • The M+1 peak can be disregarded
  • Fragments should be shown with a positive sign
  • The x-axis is mass and the y-axis is relative abundance
99
Q

Are Carboxylic acids polar or non polar?

A

Polar, as electrons are drawn from the carbon atoms in the carbonyl groups towards the more electronegative oxygen atoms. This makes them very soluble.

100
Q

Disadvantages of using biodegradable polymers

A
  • They need the right conditions to decompose, it won’t happen in land fill
  • More expensive
101
Q

Base hydrolysis of an Ester involves…

A

Splitting an Ester into a carboxylate salt and an alcohol under reflux with a dilute alkali like NaOH

102
Q

Test for alkenes

A

Add 2cm3 of orange bromine water to 2cm3 of your unknown hydrocarbon sample. Shake. Alkenes will decolourise bromine

103
Q

What type of molecule forms addition polymers?

A

Alkenes or substituted alkenes

104
Q

What is the equation that shows the formation of the nitronium ion (NO2+) from chemical reagents

A

HNO3 + H2SO4 -> HSO4- + H2O + NO2+

105
Q

Will polyesters and polyamides hydrolyse more easily with a base or an acid? And what are the products?

A

Polyesters: with a base to form dicarboxylic acid salt and a diol

Polyamides: with an acid to form a dicarboxylic acid and a diammonium salt

106
Q

Products if incomplete combustion

A

CO and H2O

107
Q

Explain the relative resistance to bromination of benzene compared to phenol and cyclohexene

A

Benzene electrons are delocalised
In phenol, a lone pair of electrons on the OH group is partially delocalised into the ring
In cyclohexene, electrons are localised between carbons.
Benzene has a lower electron density than cyclohexene and phenol so cannot polarise or induce a dipole in Br2

108
Q

Aldehyde + tollens reagent =

Product and colour

A

Carboxylic acid and silver mirror

109
Q

What is a diazonium ion?

A

N triple bond N, the N closest to the carbon has a positive charge

110
Q

Problems with making a chiral drug and how to overcome it

A

Production of single isomer is expensive. One of the isomers may have harmful side effects.
Overcome by using enzymes or chiral synthesis

111
Q

What is the formula of the organic salts formed when a gas scrubber removes HCl or H2S

A

R-NH3+Cl- or R-NH3+HS-

112
Q

What is GC-MS

A

Gas chromatography- Mass spectra

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