alkanes

Question 1

what are alkanes

Answer 1

saturated hydrocarbons containing single C-C AND C-H bonds made of sigma bonds
they are CnH2N+2

Question 2

variations in boiling points

Answer 2

induced dipole dipole interaction happen between alkane chains, alkanes are affected by chain length and branching
boiling points increase with carbon to carbon chain length as they have stronger london forces so more energy
more branching reduce the surface area of contact , fewer london forces, less energy to overcome

Question 3

what shape is alkanes

Answer 3

tetmedrahal at 109.5

Question 4

what are reactions of alkanes?

Answer 4

alkanes have a low reactivity due to high bond entropy of the carbon single bonds and low priority of the sigma bonds

Question 5

Combustion of alkanes

Answer 5

alkanes make good fuels as they release a lot of energy when burned

Question 7

complete combustion

Answer 7

They undergo complete combustion with sufficient oxygen present to produce carbon dioxide and water
CH4 + 2o2 = CO2 + H2O

Question 8

incomplete combustion

Answer 8

if there is little oxygen, the combustion is incomplete and carbon monoxide is produced with water
2CH4 + 3O2 = 2CO + 4H2O

Question 9

Carbon monoxide

Answer 9

carbon monoxide is a toxic predict that is dangerous to humans as it’s all us and colourless. It can replace oxygen in the blood starving the brain and causing people to suffocate.

Question 10

what is also released in alkane combustion?

Answer 10

Oxides of nitrogen and carbon monoxide which can react with water and cause acid rains but it can be removed by using a catalytic converter which uses a rhodium catalyst to convert harmful products into more stable products like carbon dioxide

Question 11

What is chlorination of alkanes?

Answer 11

alkanes = haloalkanes but with UV light + halogen
UV light breaks down the hydrogen bonds (homolytic fission) producing free radicals

Question 12

Part one of three radical stop substitution free radical substitution

Answer 12

initiation the bond is broken to form two free radicals e.g.
Cl2 = 2Cl degree
with uv light

Question 13

Stage two of free radical substitution

Answer 13

propagation e.g.
ch4 + cl = ch3 + hcl
ch3 + cl2 = ch3cl + cl

Question 14

stage four of free radical substitution

Answer 14

termination only two radicals reacting with each other
2cl = cl2. cl + ch3 =ch3cl
2ch3 = c2h6