Alkanes

Question 1

What is free radical substitution?

Answer 1

A reaction involving the substitution of atoms in a molecule by free radicals.

Question 2

What role does UV light play in free radical substitution?

Answer 2

UV light provides the energy to break covalent bonds, creating two radicals.

Question 3

What is a radical?

Answer 3

An atom or molecule with a single unpaired electron, represented by a (.) in equations.

Question 4

What occurs during the initiation step of free radical substitution?

Answer 4

The halogen is broken apart by UV light to create two free radicals.

Question 5

What happens during the propagation step?

Answer 5

The reaction propagates through two steps, also known as a chain reaction.

Question 6

What is the termination step in free radical substitution?

Answer 6

Two radicals collide to form a molecule with all electrons paired, stopping the reaction.

Question 7

What can two methane radicals create?

Answer 7

They can react to create ethane.

Question 8

What are hydrocarbons?

Answer 8

Hydrocarbons are molecules that only contain carbon and hydrogen.

Question 9

What is combustion?

Answer 9

Combustion is when something reacts with oxygen.

Question 10

What is the general equation for the combustion of alkanes?

Answer 10

Alkane + Oxygen = Carbon dioxide + Water.

Question 11

What is the balanced equation for the combustion of methane?

Answer 11

CH4(g) + 2O2(g) = CO2(g) + 2H2O(L)

Question 12

What is free radical substitution?

Answer 12

A reaction involving the substitution of atoms in a molecule by free radicals.

Question 13

What role does UV light play in free radical substitution?

Answer 13

UV light provides the energy to break covalent bonds, creating two radicals.

Question 14

What is a radical?

Answer 14

An atom or molecule with a single unpaired electron, represented by a (.) in equations.

Question 15

What occurs during the initiation step of free radical substitution?

Answer 15

The halogen is broken apart by UV light to create two free radicals.

Question 16

What happens during the propagation step?

Answer 16

The reaction propagates through two steps, also known as a chain reaction.

Question 17

What is the termination step in free radical substitution?

Answer 17

Two radicals collide to form a molecule with all electrons paired, stopping the reaction.

Question 18

What can two methane radicals create?

Answer 18

They can react to create ethane.

Question 19

How many sigma bonds does each carbon form in alkanes?

Answer 19

Each carbon forms 4 sigma bonds.

Question 20

What is the bond angle in an alkane?

Answer 20

The bond angle is 109.5 degrees.

Question 21

What is the 3D shape of an alkane?

Answer 21

The 3D shape of an alkane is tetrahedral.

Question 22

How do we identify an alkane at GCSE level?

Answer 22

We identify an alkane by its double bond.

Question 23

How many sigma bonds does each carbon form in alkenes?

Answer 23

Each carbon atom forms 3 sigma bonds.

Question 24

What is the bond angle in an alkene?

Answer 24

The bond angle is 120 degrees.

Question 25

What is the shape around an alkene?

Answer 25

The shape around an alkene is trigonal planar.

Question 26

What are the leftover carbon electrons in an alkene called?

Answer 26

They are known as a P-orbital.

Question 27

What do two P-orbitals overlap to form?

Answer 27

They overlap to form a pi bond.

Question 28

What forms a double bond in alkenes?

Answer 28

A pi bond and a sigma bond come together to form a double bond.

Question 29

Which bond is weaker, pi bond or sigma bond?

Answer 29

A pi bond is weaker than a sigma bond.

Question 30

Why is a sigma bond stronger than a pi bond?

Answer 30

In a sigma bond, the orbitals overlap and point directly at each other, whereas in a pi bond they aren’t overlapped nor facing each other.

Question 31

What is the shape of P-orbitals when viewed in 3D?

Answer 31

P-orbitals are dumbbell shaped.