C10

Question 1

What are alkenes ?

What is the formula for the homologous series?

Answer 1

Alkenes are hydrocarbons with a double carbon-carbon bond. The general formula for the homologous series of alkenes is CnH2n

Question 2

Why are alkenes refered to as unsaturated?

Answer 2

Alkene molecules are unsaturated because they contain two fewer hydrogen atoms than the alkane with the same number of carbon atoms.

Question 3

Who are The first four members of the homologous series of alkenes

Answer 3

ethene, propene, butene and pentene.

You must he able to draw the displayed formula for this

Question 4

What is the funcyional group of am alkene molecule?

Answer 4

Alkenes are hydrocarbons with the functional group C=C

Question 5

What does a functional group do

Answer 5

A functional group is a group of atoms in a molecule that determine how the molecule typically reacts.

Question 6

How do alkenes react with oxygen in combustion reactions

Answer 6

Alkenes react with oxygen in combustion reactions in the same way as other hydrocarbons. Unlike other hydrocarbons they tend to burn in air with smoky flames because of incomplete combustion. This means along with carbon dioxide and water they also produce carbon and carbon monoxide. Less energy is also released during combustion.

Question 7

How do alkenes react most of the time.

Answer 7

Most of the time alkenes react through addition reactions where the double carbon bond will open to leave a single bond and a new atom is added to the carbon

Question 8

What is a homologous series?

Answer 8

A homologous series is a family of organic compounds who react in a similar way and share the same functional group.

Question 9

What is hydrogenation of alkenes?

Answer 9

Hydrogenation is the addition of hydrogen
When hydrogen reacts with the carbon-carbon double bond the reaction opens up the double bond to the hydrogen and form the equivilant saturated alkane.
This must happen in the presence of a catalyst
(You must he able to draw the displayed formula for this)

Question 10

What happens when steam reacts with alkenes?

Answer 10

This is another addition reaction
Water is added across the double bond and an alcohol is formed
A catalyst must be present
(You must he able to draw the displayed formula for this)

Question 11

What happens when halogen react with alkenes?

How can this reaction be used by scientists?

Answer 11

This ia another addition reaction
The carbons in the double C-C bond become bonded to 2 halogen atoms (bromine, chlorine iodine)
(You must he able to draw the displayed formula for this)
This can be used as a chemical test for alkenes:
When orange bromine water is added to a staturated alkane no reaction will happen and the solution stays bright orange
However when orange bromine water is added to a ustaturated alkene the bromine reacts with the carbon-carbon double bond and adds across the double bond making a colourless dibromo compound.

Question 12

What is the general formula of an alcohol ?

Answer 12

CnH2n+1OH

Question 13

What is the functional group of an alcohol?

Answer 13

-OH

Question 14

What are the first 4 members of the homologous series of alcohols

Answer 14

Methanol
Ethanol
Propanol
Butanol

Question 15

What are the properties of alcohol and how do they interact with the environment

Answer 15

Flammable: undergo complete combustion in air ( produces CO2 and water )
Soluble in water ( solutions have a neutral pH )
React with sodium, one of the products is hydrogen
Can be oxidised by reacting with oxygen ( e.g from air ) to produce a carboxylic acid

Question 16

Uses of alcohols

Answer 16

Alcohols such as methanol and ethanol are used as solvents in industry because they dissolve most things and things that water cant dissolve e.g hydrocarbons, oils and fats
First 4 can be used as fuels e.g in spirit burners - it burns cleanly and without a smell
Ethanol can be used in alcoholic drinks from fermentation

Question 17

What is the word equation for fermentation

Answer 17

Sugar -(yeast)–> ethanol + carbon dioxide

Question 18

What are the conditions for fermentation and why

Answer 18

Happens fastest at 37°C
Best in a slightly acidic solution
Under anaerobic conditions
Enzyme yeast works best in these conditions

Question 19

Carboxylic acid functional group

Answer 19

-COOH

Question 20

Foret 4 members of a homologous series of carboxylic acids

Answer 20

methanoic acid
ethanoic acid
propanoic acid
butanoic acid.

Question 21

What do carboxylic acids produce when they react with a carbonate

Answer 21

Salt, water and carbon dioxide
Salts formed end in ‘ anoate ‘
E.g methanoic acid forms a methanoate or ethanoic acid forms ethanoate

Question 22

What does ethanoic acid + sodium carbonate produce

Answer 22

Ethanoic acid + sodium carbonate = sodium ethanoate + water c carbon dioxide

Question 23

What do carboxylic acids do when dissolved in water

Answer 23

They ionise to produce H+ ions
Don’t ionise completely, they just form weak acidic solution
Carboxylic acids are weak acids ( higher pH )

Question 24

Word equation for alcohol + carboxylic acids

Answer 24

Alcohol + carboxylic acids -(acid catalyst)–> ester + water

Question 25

How is ethyl ethanoate made ( only specifc one we need to know )

Answer 25

Ethanoic acid + ethanol -(acid catalyst)–> ethyl ethanoate + water

Question 26

Function group for esters ( not mentioned on spec or CGP )

Answer 26

-COO

Question 27

Displayed formula for a carboxylic acid

Answer 27

Ethanoic acid:
       H        O
        |      =
H - C - C 
        |      \
       H      OH