Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

national 5 chemistry > Homologous series > Flashcards

Homologous series Flashcards

1
Q

How many bonds can carbon form?

A

Carbon can only ever form 4 bonds (valency 4). It will not form more or less bonds than this as it would not obtain a complete electron energy level.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How many bonds can hydrogen form?

A

Hydrogen can only form 1 bond (valency 1). It will not form more or less bonds than this as it would not obtain a complete electron energy level.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is a hydrocarbon?

A

A hydrocarbon is a compound made from hydrogen and carbon only.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Describe what is meant by a saturated compound.

A

The alkanes are a homologous series of hydrocarbons that have single covalent bonds only between their carbon atoms.

These are saturated hydrocarbons and the name of all the members of the alkane homologous series ends in -ane. e.g. butane.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Describe what is meant by a unsaturated compound.

A

The alkenes are a homologous series of hydrocarbons that contain at least one carbon-carbon double bond.

Alkenes are unsaturated hydrocarbons and the name of all the members of the alkene homologous series ends in -ene.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What does the first part of the name of a hydrocarbon tell us?

A 
The first part of the name of hydrocarbon tells you the number of carbon atoms joined together in a straight chain.
meth:1
eth:2
prop;3
but:4
pent:5
hex:6
hept:7
Oct:8
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the homologous series?

A

A homologous series is a family of compounds with similar chemical properties who share the same general formula.
3 different homologous series of hydrocarbons include:
Alkanes
Alkenes
Cycloalkanes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are the three ways to write or draw the formula of a hydrocarbon?

A
  1. Full structural formula
  2. Shortened structural formula
  3. Molecular formula
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is shown in a full structural formula?

A

This shows all the atoms and all the bonds in a molecule.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is shown in a shortened structural formula?

A

This shows the number of hydrogen atoms attached to each carbon atom (in order). The bonds between the carbon atoms may or may not be shown.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is shown in a molecular formula?

A

This shows the type and total number of each atom only.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the general formula for alkanes?

A

CnH2n+2 (where n = number of carbon atoms)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are the uses of alkanes?

A

Alkanes are:

  • Used as fuels e.g. methane (natural gas) , propane and butane (bottled gas), petrol, kerosine (aircraft fuel) and diesel.
  • Used as chemicals such as solvents, lubricants and waxes.
  • Converted into alkenes by a process known as catalytic cracking. Alkenes are important chemicals in industry as they are used to manufacture many other chemicals and are referred to as feedstock chemicals.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Are alkanes soluble or insoluble in water?

A

Alkanes are insoluble in water.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the first member of the alkene family called?

A

The first member of the alkene family is ethene as there must be a minimum 2 carbon atoms present to have a double bond present.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the general formula for alkenes?

A

CnH2n (where n = number of carbon atoms)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What are the uses of alkenes?

A

Alkenes are very useful feedstock chemicals that are used in the making of:

  • plastics (polymers)
  • ethanol (alcohol) and ethanoic acid (vinegar)
  • pesticides
  • medicine
  • toiletries and cosmetics etc
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Are alkenes soluble or insoluble in water?

A

Alkenes are insoluble in water.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Describe cycloalkanes.

A

Cycloalkanes are a homologous series of saturated, cyclic (C atoms joined in rings) hydrocarbons.

The name of all the members of the cycloalkane homologous series starts with cyclo- and ends in -ane.

20
Q

What is the first member of the cycloalkane family?

A

The first member of the cycloalkane family is cyclopropane as a minimum of 3 carbon atoms are required to form a ring.

21
Q

What is the general formula for cycloalkanes?

A

CnH2n (where n=number of carbon atoms)

22
Q

What is an isomer?

A

Compounds with the same molecular formula but different structural formula are called isomers.

23
Q

Which two homologous series are isomers of each other?

A

Alkenes and cycloalkanes with the same number of carbon atoms are isomers of each other.

24
Q

What is a functional group?

A

A functional group is an atom, group of atoms or types of bonds within a molecule that gives the compound its characteristic chemical properties.
e.g.
The functional group of an alkene is the double carbon to carbon covalent bond.

25
Q

What are the rules for naming branched alkanes?

A
  1. Identify and name the longest chain. (This will form the main part of the name.)
    2.Identify the branche(s) and number the carbon atoms in the longest chain, starting from the end nearest to the branch.
    3.Name and number the branche(s). (each branch will have to be named and numbered)
  2. Seperate numbers by commas and letters and numbers by a hyphen.
    use prefixes di-,tri-,etc when a branch appears more than once.
26
Q

What are the rules for naming alkenes and branch chained alkenes?

(note these rules apply to alkenes and molecules containing other functional groups (such as alcohols)

A
  1. The position of the double bond must be indicated by a number. If the double bond can appear in more than one different place. The carbon nearest the functional group is numbered the first carbon atom.
  2. If a functional group, such as a double bond, and a branch is present, the longest chain is numbered from the end nearest the functional group and the branch(es) allocated accordingly.
27
Q

What is meant by viscosity?

A

A measure of how thick or runny a substance is. A substance that is very viscous is thick like syrup, a substance that is not very viscous is runny like water.

28
Q

What is meant by flammability?

A

A measure of how easily a substance will ignite. (high flammability means the substance will ignite easily.)

29
Q

What is meant by volatility?

A

A measure of how easily a substance will evaporate. (Low volatility means it will not evaporate easily)

30
Q

Which physical properties show a trend as you go down a homologous series i.e as the carbon chain increases?

A

The following physical properties all show a trend as you go down a homologous series i.e. as the carbon chain length increases:
boiling point
volatility
flammability
viscosity
colour (becomes darker as you descend a homologous series)

31
Q

Describe the trend in boiling point as you go down a homologous series.

A

The boiling point increases as you go down a homologous series.

32
Q

Why does the boiling point increase with molecular size?

A

The boiling point increases as you go down a homologus series because as the size of a molecule increases there are more attractive forces between molecules. These attractive forces are weak and are called intermolecular forces or Van der Waals forces of attraction. The intermolecular forces are greater, the bigger the molecule, requiring more energy to separate larger molecules, thus the boiling point increases with molecular size.

33
Q

Describe the trend in volatality in a homologus series.

A

Volatility decreases as you go down a homologous series. This is because as molecules get larger there are more intermolecular forces that need to break in order to evaporate, requiring more energy.

34
Q

Describe the trend in flammability in a homologous series.

A

Flammability decreases as you go down a homologous series. This is because molecules have to evaporate and mix with oxygen before they can burn. We have already seen that larger molecules require more energy to evaporate due to stronger intermolecular forces.

35
Q

Describe the trend in viscosity in a homologous series.

A

Viscosity increases down a homologous series as the longer chains become entangled making it harder for the molecule to move past each other and so they so do not flow so freely as smaller molecules.

36
Q

What are the two important reactions with hydrocarbons?

A

Two important reactions that alkanes, cycloalkanes and alkenes do are combustion and reacting with bromine.

37
Q

Describe combustion of hydrocarbons.

A

All hydrocarbons undergo complete combustion to produce carbon dioxide and water.

38
Q

Describe incomplete combustion.

A

Incomplete combustion, takes place in a limited air or oxygen supply. The products of incomplete combustion include carbon monoxide and/or unburnt carbon (soot).

39
Q

Which hydrocarbons are more reactive?

A

Saturated compounds such as the alkanes are quite unreactive as the carbon atoms are bonded to the maximium number of atoms allowed by the valency and one or more of these atoms would have to be removed or substituted to allow reaction with another substance. Unsaturated compounds such as alkenes are more reactive as the carbon atoms can bond to other atoms across the double bond.

40
Q

What is the addition reaction of bromine with alkenes used for?

A

The addition reaction of bromine with alkenes is used to distinguish between saturated and unsaturated compounds such as alkanes and alkenes. Shake the compound with bromine solution, if the bromine solution decolourises rapidly (goes from orange to colourless), the compound is unsaturated but if the orange colour remains the compound is saturated.

41
Q

What can alkenes undergo addition reactions with?

A

Halogens (group 7 elements)
Hydrogen
Hydrogen halides
Water

42
Q

When naming carbon compounds containing halogens what is the functional group and how does the name change?

A 
When naming carbon compounds containing halogens the halogen becomes the functional group and the name ending changes as follows:
Fluorine becomes fluoro
Chlorine becomes chloro
Bromine becomes bromo
Iodine becomes iodo
43
Q

Describe the addition reaction of a halogen (halogenation) with an alkene.

A

Aswell as bromine, other halogens (group 7 elements) can add across the double to produce a halogenoalkane.

44
Q

Describe the addition of hydrogen (hydrogenatation) with an alkene.

A

The addition of hydrogen to an alkene produces the corresponding alkane.

45
Q

Describe the addition of a hydrogen halide.

A

A hydrogen halide is a compound of hydrogen with any halogen e.g. HBr. They add across the double bond to form halogenoalkanes. The hydrogen halide can give two products (isomers) as it can add across the double bond in two different ways if the double bond is not in the middle of the alkene molecule.

46
Q

Describe the addition of water (hydration) with an alkene.

A

When water is added to an alkene (e.g. ethene) an alcohol is formed. This reaction is carried out using a catalyst and water (in the form of steam).

national 5 chemistry (42 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions