ALKANES

Question 1

What is an alkane

Answer 1

a fully saturated hydrocarbon

Question 2

What shape are alkanes

Answer 2

tetrahedral around each carbon

bonding angles are 109.5

Question 3

Why are alkanes used as fuels

Answer 3

they release large amounts of energy and burn quite readily

alkanes burn in plentiful oxygen completely*

Question 4

What are alkanes used for in real life

Answer 4

used to power vehicles and to generate electricity by combustion

Question 5

How to work out formula of a hydrocarbon being burnt

Answer 5

use the information given to write a volume ratio and deduce from there by balancing the equation

Question 6

what is produced from incomplete combustion of alkanes

Answer 6

Carbon monoxide or Carbon(soot)

Question 7

What happens in the initiation step of a free radical chain reaction

Answer 7

Radicals are produced using visible or UV light by homolytic fission

Question 8

What happens in the propagation step of a free radical chain reaction

Answer 8

A radical can react with a non radical molecule, this creates a new radical which can react with other non radicals, this is called a chain reaction

Question 9

What happens in the termination step of a free radical chain reaction

Answer 9

2 radicals react to form a non radical, this ends the chain reaction

Question 10

Give the free radical substitution mechanism to make chloromethane

Answer 10

I Cl2 –>(UV) Cl. + Cl.

P Cl. + CH4 –> CH3. + HCl
CH3. + Cl2 –> CH3Cl + Cl.

T CH3. + Cl. –> CH3Cl

Question 11

How can impurities be made in free radical reactions and how can this be reduced

Answer 11

An excess of radicals can react with the desired product to undergo further reactions, and the product of this can react even further

can be prevented by adding excess of the non radical molecule of the reaction

Question 12

How can isomers be formed in free radical substitutions

Answer 12

as the radical will react anywhere on the hydrocarbon chain