organic chemistry

Question 1

Why can carbon form rings and very long chains?

Answer 1

• a carbon atom has 4 electrons in its outer shell, so it forms 4 covalent bonds
• carbon-carbon bonds are relatively strong and non polar

Question 2

Define empirical formula

Answer 2

Simplest whole number ratio of atoms in a molecule

Question 3

Define molecular formula

Answer 3

The actual number of atoms of different elements in a molecule

Question 4

Define displayed formula

Answer 4

Shows every atom and bond in a molecule

Question 5

Define structural formula

Answer 5

Shows arrangement of atoms in a molecule without showing every bond

Question 6

Define skeletal formula

Answer 6

Drawn as lines with each vertex being a carbon atom
Carbon atoms are not drawn

Question 7

Define structural isomerism

Answer 7

Molecules have the same molecular formula but different structural formula

Question 8

Define positional isomerism

Answer 8

Functional group attached to the main chain at a different place

Question 9

Define functional group isomerism

Answer 9

Same atoms but a different functional group due to a different arrangement of atoms

Question 10

Define chain isomerism

Answer 10

Hydrocarbon chain organised differently

Question 11

Define stereoisomerism

Answer 11

Molecules have the same structural and molecular formula but a different arrangement of atoms in space

Question 12

What is E-Z isomerism caused by?

Answer 12

The limited rotation of C=C double bonds

Question 13

What is the process which separates the components of crude oil?

Answer 13

Fractional distillation

Question 14

Method of crude oil separation

Answer 14

• mixture is vapourised and fed into fractioning column
• vapours rise, cools and condense
• products are siphoned off for different uses

Question 15

Short chain hydrocarbons have a ……… boiling point than long chain hydrocarbons

Answer 15

Lower

Question 16

Thermal cracking conditions

Answer 16

1200K
7000kPa (70atm)

Question 17

Catalytic cracking conditions

Answer 17

720K
Normal pressure
Zeolite catalyst

Question 18

Alkanes undergo complete combustion to produce:

Answer 18

Carbon dioxide
Water

Question 19

Incomplete combustion of alkanes produces:

Answer 19

Carbon monoxide
Water

Question 20

What’s catalyst do catalytic converters use?

Answer 20

Rhodium catalyst

Question 21

Carbon particulates can cause:

Answer 21

Serious respiratory problems

Question 22

Sulphur impurities can be removed with what reaction?

Answer 22

Flue gas desulphurisation
Calcium oxide and gypsum are used in the process

Question 23

What are the three reactions involved in free radical substitution?

Answer 23

1. Initiation
2. Propagation
3. Termination

Question 24

What happens in the initiation step of a free radical substitution reaction?

Answer 24

The halogen is broken down using UV light
Ie. Cl2 -> 2Cl*

Question 25

What happens in a propagation step?

Answer 25

A hydrogen atom is replaced and the Cl* radical reformed as a catalyst

Question 26

What happens in the termination step of a free radical substitution reaction?

Answer 26

Two radicals join to end the chain reaction and form a stable product Ie. *CH3 + *CH3 - C2H6

Question 27

Why do halogenoalkanes contain polar bonds?

Answer 27

The halogens are more electronegative than carbon atoms, and electron density is drawn towards the halogen forming ∂+ and ∂- regions

Question 28

Define a nucleophile

Answer 28

An electron pair donor

Question 29

Examples of common nucleophiles

Answer 29

CN:- :NH3 -:OH

Question 30

What can nucleophilic substitution reactions be used to produce

Answer 30

Amines or alcohols

Question 31

The greater the Mr of the halogen in the polar bond, the …….. the bond enthalpy

Answer 31

Lower Meaning that it can be broken down more easily, therefore rate of reaction for these halogenoalkanes is faster

Question 32

Nucleophilic substitution reactions can only occur for ……….. halogenoalkanes

Answer 32

1º (primary) and 2º (secondary)

Question 33

Elimination reactions occur when a halogenoalkanes is heated to:

Answer 33

High temperatures, under alcoholic conditions

Question 34

In elimination reactions, the nucleophile acts as a:

Answer 34

Base And accepts a proton, removing a hydrogen atom from the molecule This results in the elimination of the halide too, producing a carbon-carbon double bond

Question 35

Elimination reactions only occur from ………. Halogenoalkanes

Answer 35

2º and 3º

Question 36

Ozone in the atmosphere absorbs:

Answer 36

UV radiation

Question 37

What the problem with CFCs?

Answer 37

The absorb UV radiation, breaking down the carbon-hydrogen bonds to form free radicals that can catalyse oxygen depletion