Alkanes

Question 1

What are alkanes

Answer 1

Alkanes are a homologous series made up of saturated molecules which are joined by sigma bonds/single covalent bonds

Question 2

are alkanes unreactive

Answer 2

yes

Question 3

what is the general formula for alkanes

Answer 3

Cn H2n+2

Question 4

what is a sigma bond

Answer 4

​its a single covalent bond ​formed when​ two orbitals overlap end-to-end

Question 5

what is a covalent bond

Answer 5

a shared pair of electrons

Question 6

in an alkane how many sigma bonds does each carbon atom have?

Answer 6

4

Question 7

each bond angle is

Answer 7

109.5 degrees (tetrahedral)

Question 8

how is crude oil seperated into fractions

Answer 8

fractional distillation

Question 9

why do the boiling points of alkanes increase?

Answer 9

London forces hold molecules together in solids and liquids but once broken the molecules move apart and the alkane becomes a gas. The greater the intermolecular forces the higher the boiling point.

Question 10

If the chain length increases will the surface contact increase

Answer 10

Yes

Question 11

Do you need more or less energy to overcome the greater london forces

Answer 11

more

Question 12

Isomers of alkanes have the same molecular mass true or false

Answer 12

true

Question 13

Do branched isomers have higher or lower boiling points than straight-chained isomers?

Answer 13

Lower

Question 14

What are the factors that make alkanes unreactive?

Answer 14

-The C-C and C-H sigma bonds are strong
-The C-C bonds are non-polar
-The elecronegativity of carbon and hydrogen is so similar that it is considered non-polar

Question 15

What do all alkanes react with?

Answer 15

A plentiful supply of oxygen to produce carbon dioxide and water

Question 16

What is combustion?

Answer 16

It is a chemical reaction that involes burning the organic compounds

Question 17

what do all combustion reactions give out?

Answer 17

heat

Question 18

What are 3 reasons alkanes are used as fuels?

Answer 18

-They are readily available
-Easy to transport
-Burn in plentiful supply of oxygen without releasing toxic products

Question 19

What is carbon monoxide?

Answer 19

A colourless odourless highly toxic gas

Question 20

When does incomplete combustion occur?

Answer 20

When there is a limited supply of oxygen usually in a closed system.

Question 21

What happens in the presence of sunlight (UV)

Answer 21

alkanes react with halogens

Question 22

3 stages of the mechanism

Answer 22

initiation,propagation and termination

Question 23

What happens in initiation?

Answer 23

the covalent bond in a halogen molecule is broken by homolytic fission. Each halogen atom takes one electorn from the pair forming two highly reactive molecules

Question 24

What happens in propagation?

Answer 24

In the first step a halogen radical reacts with a C-H bond forming an alkyl radical and a molecule of hydrogen something

In the second step each alkyl radical reacts with another halogen molecule to form..

Then the new halogen radical reacts with another alkane and it goes on and on.

Question 25

What happens in termination?

Answer 25

two radicals colide to form molecules with all electrons paired

Question 26

What is further substitution

Answer 26

different possible monosubstitutes