Module 4

Question 1

Empirical formula

Answer 1

Simplest whole number ratio of elements in a compound

Question 2

Molecular formula

Answer 2

The actual number of atoms of each element in a compound

Question 3

General formula

Answer 3

Formula which covers a homologous series

Question 4

Structural formula

Answer 4

Minimal level of detail needed to draw something

Question 5

Displayed formula

Answer 5

Shows all of bonds

Question 6

What is the priority list of order for iupac namunclature

Answer 6

• Carboxylic acid, aldehyde,ketone,alkene, alcohol, halogen

Question 7

Homologous group

Answer 7

• compounds with same functional group
• but each successive member differs by ch2

Question 8

Functional group

Answer 8

part of molecule responsible for its chemical reactions

Question 9

hydrocarbon

Answer 9

molecule containing carbon and hydrogen only

Question 10

saturated compound

Answer 10

contains single bonds only

Question 11

unsaturated compound

Answer 11

contains atleast one carbon to carbon multiple bond

Question 12

aromatic

Answer 12

contains a benzene ring

Question 13

aliphatic

Answer 13

contains carbon in a straight chain, branched chain or non-aromatic ring

Question 14

structural isomer

Answer 14

compounds with same molecular formula but different structural formula

Question 15

stereoisomerism

Answer 15

compounds with same structural formula but different arrangement of atoms in space

Question 16

homolytic fission

Answer 16

where covalent bond breaks and electrons go to each atom forming 2 radicals

Question 17

heterolytic fission

Answer 17

covalent bond breaks and both electrons go to one atom forming 2 ions

Question 18

radical

Answer 18

highly reactive species with an unpaired electron

Question 19

curly arrow

Answer 19

shows movement of pair of electrons

Question 20

nucleophile

Answer 20

electron pair donor

Question 21

electrophile

Answer 21

electron pair acceptor

Question 22

describe bonding in alkanes

Answer 22

-sigma bonds
- which can rotate and are formed by head on overlap of neighbouring p-orbitals

Question 23

what is the shape in alkanes?

Answer 23

tetrahedral shape 109.5

Question 24

why do increased chain lengths increase boiling point in alkanes?

Answer 24

• increased chain length increases number of carbons
• increased points of surface contact
• so stronger induced dipole dipole interactions between molecules
• which needs more energy to overcome

Question 25

why does increased branching decrease boiling point in alkanes?

Answer 25

- increased branching decreases points of surface contact between molecules - weaker induced dipole dipole interactions between molecules - which needs less energy to overcome

Question 26

Why are alkanes very unreactive?

Answer 26

- due to high bond enthalpies - and low polarity of C-C and C-H

Question 27

why are alkanes used as fuels?

Answer 27

- as large amount of energy is released with bond breaking

Question 28

what are the products of complete combustion?

Answer 28

- CO2 and H2O

Question 29

what are the products of incomplete combustion?

Answer 29

- CO and H2O - Carbon dioxide and carbon - CO is poisonous - CO2 and H2O are greenhouse gases

Question 30

what is needed for alkane and halokane to react

Answer 30

- Halogen - UV light - High temp

Question 31

What is the mechanism called of halogen and alkane reaction

Answer 31

- free radical substitution

Question 32

What are the limitations of free radical substitution?

Answer 32

- multi substitution can occur - substitution occurs at different positions on carbon chain producing mixture of isomers

Question 33

why are alkenes reactive

Answer 33

- has sigma bond which is stronger and weaker pi bond which restricts rotation - during reactions weaker pi bond breaks and stronger sigma bond remains intact

Question 34

what is shape around alkene?

Answer 34

trigonal planar- 120 degrees

Question 35

describe bonding in alkene

Answer 35

- sideways overlap of 2 p orbitals on each carbon forms a pi bond above and below the plane of the molecule

Question 36

When can a molecule exhibit e/z isomerism?

Answer 36

if it has: - a carbon carbon double bond which restricts rotation - has 2 different groups attached to each carbon in carbon carbon double bond

Question 37

when can molecule exhibit cis/trans isomerism?

Answer 37

- when 2 substituents are the same on each carbon (one on each)

Question 38

what is percentage atom economy for addition reactions?

Answer 38

- 100%

Question 39

Why are addition polymers non biodegradable?

Answer 39

- they have strong C-C bonds

Question 40

How to deal with addition polymers?

Answer 40

- separate into types by sorting and recycle - crack them into monomers and use them as feedstock for other reactions - burn waste to generate electricity - landfill

Question 41

why is pentan-2,2-diol more soluble than pentan-1-ol?

Answer 41

pentan-2,2-diol has more hydroxy groups and so forms more hydrogen bonds with water

Question 42

why are haloalkanes polar

Answer 42

- the halogen is more electronegative than the carbon

Question 43

how to measure rate of hydrolysis

Answer 43

- heat haloalkane with water in presence of silver nitrate in ethanol - silver ion reacts with the halide ion to form a coloured ppt - measure time taken

Question 44

why is C-I faster rate of hydrolysis than C-Br

Answer 44

- Bond enthalpy of C-I is weaker than C-Br so breaks more easily and so faster hydrolysis

Question 45

how is conc of ozone maintained in atmosphere?

Answer 45

O3->O2+O reversible reaction

Question 46

uses of CFCs eg Cl3FC

Answer 46

refrigerants, dry cleaning fluids, aerosol propellants

Question 47

useful properties of CFCs

Answer 47

-low reactivity - non-toxic -non-flammable -volatile

Question 48

why are CFCs bad?

Answer 48

- produce chlorine radicals which catalyse destruction of ozone

Question 49

why is ozone good

Answer 49

- absorbs UV light from atmosphere

Question 50

how to purify liquid sample:

Answer 50

- add base to neutralise acid - transfer contents to separating funnel and shake - less dense layer at top and more dense at bottom - run of required layer - dry organic layer with MgSO4 - redistill the liquid to further purify it and collect

Question 51

how does ir spectroscopy work

Answer 51

- molecules absorb ir radiation - make bonds vibrate

Question 52

green house gases such as ch4 and co2 and h2o absorb ir radiation

Answer 52

causes global warming

Question 53

uses of ir spectroscopy

Answer 53

- monitor gases causing air pollution - modern breathalysers to monitor ethanol