Ocr As Level Chemistry

Front 1

When hydrocarbons are burnt completely in oxygen they form carbon dioxide and water

C4H10 + 6.5 O2 --> 4 CO2 + 5 H2O

Back 1

When hydrocarbons are burnt incompletely in oxygen they form carbon monoxide and water

C4H10 + 4.5 O2 --> 4 CO + 5 H2O

Front 2

Alkanes have a general formula of CnH2n+2 where n is the number of carbon atoms

Back 2

Names of all alkanes end in -ane. Identify the longest chain then add on any branches.

E.g- methane or ethane and 2-methylpropane if the methyl group is on the second carbon

Front 3

Common prefix

1 Carbon: Meth
2 Carbon: Eth
3 Carbon: Prop
4 Carbon: But
5 Carbon: Pent
6 Carbon: Hex
7 Carbon: Hept
8 Carbon: oct

Back 3

A Homologous Series is a set of organic componds with the same functional group, but with each successive member differing by CH2

Front 4

A chain length increases the boiling point increases due to increased van der walls forces between molecules

Back 4

Short chain alkanes have low boiling points due to weak van der walls forces

Front 5

Alkanes are saturated molecules as they only contain single carbon bonds

Back 5

Main use of alkanes is combustion to produce energy

Uses include; bottled gas, vehicle and aircraft fuel

Front 6

Isomers are compounds with the same molecular formula but a different arrangement of atoms

There different structures effect the boiling points and soluablity

This is because branched compounds have weaker van der walls forces as there are less points of contact so lowers the boiling point

Back 6

Alkanes are ISOMERISED (adding of branches normally) to raise the octane number. This is why branched alkanes are preferred over straight chain as they burn more effectively

Front 7

Cracking of alkanes will form shorter chained alkanes and alkenes

Back 7

Standard conditions:

298 kelvin
1 atmosphere

Front 8

An ALIPHATIC hydocarbon is a hydrocarbon that is either straight chained or branched

An ALICYCLIC hydrocarbon is a hydrocarbon with the carbons formed in a ring

Back 8

Alkenes are a group of hydrocarbons containing at least one carbon-carbon double bond

They are unsaturated so can form bonds with other elements

Front 9

Alkenes have a general formula of CnH2n where n is the number of carbon atoms

Back 9

When naming a alkene the prefix (meth, eth etc.) then the number of the carbon that the double bond is connected to, and finally the prefix 'ene' For example pent-1-ene, pent-2-ene or pent-3-ene depending on the location of the double bond.

Front 10

The pi bond is the bond that breaks during reactions as it has a lower bond energy

They consist of two P-orbitals that overlap sideways, Then they fuse top to top and bottom to bottom drawn as a new structure

0 0 ∞
C∞∞C ------> C∞∞C
0 0 ∞

Back 10

The sigma bond consists of two P-orbital connected long ways

C∞∞C

Front 11

The double bond consists of two types of bond:
A pi bond and a sigma bond. The pi bond is the weaker bond

Back 11

Alkenes can react with H2 in a hydrogenation reaction. This happens when the H2 breaks the double bond and saturates the alkene hence forming a alkane. For this to happen there has to be a nickel catalyst and heat (150'C)

Front 12

Alkenes can react with halogens to form a halogenoalkane. The pi bond breaks breaks and each of the halogens forms a bond with a carbon from the double bond. This is known as halogenation.

The naming of this is the name and number of the halide in front of the hydrocarbon group. Example dibromopropane or 2,3 dichlorobutane

Back 12

As well as reacting with only halogens it can react with with hydrogen-halide compounds shown as HX where X is the halogen. The reaction is the same except only one forms a carbon-halogen bond and the other forms a carbon-hydrogen bond

Naming is also the same but will not be 'di' it would be 1,bromopropane or 2,bromopropane depending which carbon the halogen goes to.

Front 13

Alkenes can react with water in the form of steam with the present of phosphoric acid (H3PO4) catalyst to form a alcohol. This is how alcohols are widely made in industry and is sometimes known as a hydration of a alkene.

Back 13

Alkenes can be formed into polymers by addition polymerisation reactions. This occurs when the C=C bond creaks and forms a bond with the adjacent carbon.

Front 14

If asked to draw a section of a polymer the amount of carbons should be double the amount of units asked

Also remember to draw brackets either side with a bond through them or if asked to draw the polymer it is the monomer in brackets with a bond through them and a n outside the brackets

Back 14

If asked to draw the monomer of a polymer than it should contain two carbons with the double bond intact

DO NOT DRAW BRACKETS AROUND THE MONOMER

Front 15

Polymers are extremely inert so take very long lengths of time to bio-degrade so alternate methods are used;

recycle
incineration
Fuel source

Back 15

Common polymers include:

Poly(ethene)
Poly(propene)
Poly(chloroethene)
Poly(phenylethene)

Front 16

E/Z isomerism can occur in certain molecules. For E/Z isomerism to occur the molecule the double bond carbon has to have two different groups on each carbon.

The E form is when the two different groups are on OPPOSITE sides (above or below the carbon)

The Z form is when the two different groups are on the SAME side of the carbon.

Back 16

Cis/Trans isomerism occurs when there is MORE than two different groups on the double bonded carbon,only then can cis/trans isomerism occur.

CIS isomerism occurs when the two LARGEST ATOMIC WEIGHT groups are on the SAME side of the double bond carbon.

TRANS isomerism occurs when the two LARGEST ATOMIC WEIGHT groups are on OPPOSITE sides of the carbon double bond .

Front 17

Alcohols have the functional group OH which joins to one of the carbons

They are named by the prefix (meth, eth, etc.) then 'an' is added (methan, ethan) then the number of the carbon that the OH group is attached too and finally the suffix 'ol' is added. Examples are propan-1-ol and propan-2-ol or butan-1-ol and butan-2-ol

Back 17

Alcohols can be placed into one of three groups; Primary, secondary or tertiary

PRIMARY alcohols form when the carbon that the OH group is attached to is bonded with ONE other carbon

SECONDARY alcohols form when the carbon that the OH group is attached to is bonded with TWO other carbon

TERTIARY alcohols form when the carbon that the OH group is attached to is bonded with THREE other carbon

Front 18

Alcohols are more soluble in water due to there ability to hydrogen bond.

There ability to hydrogen bond also means they have higher boiling points as there are stronger intra-molecular forces. An example is ethane and ethene (which cannot H-bond) are gases at room temperature compared to ethanol (which can H-bond) is a liquid

Back 18

Complete combustion of alcohol will form carbon dioxide and water, but will require less oxygen as there is a oxygen within the molecule

C2H5OH + 3 O2 ---> 2 CO2 + 3 H2O