Hydrocarbons Flashcards Preview

Chemistry Unit 3 > Hydrocarbons > Flashcards

Flashcards in Hydrocarbons Deck (19):
1

When is a sigma bond formed?

If the two half-filled atomic orbitals overlap 'end-on' or along the axis of the bond.

2

When is a pi bond formed?

If the two atomic orbitals lie perpendicular to the bond and overlap side-on.

3

Why are sigma bonds stronger than pi bonds?

Because end-on overlap of atomic orbitals is more efficient than side-on overlap.

4

Why might we expect carbon to only form 2 bonds as opposed to 4?

Because Carbon only has two half filled p orbitals.

5

What is hybridisation?

The process of mixing atomic orbitals on an atom to generate a set of new atomic orbitals called hybrid orbitals.

6

What happens to three 2p orbitals and the one 2s orbital.

They mix to form four degenerate hybrid orbitals

7

How many sigma bond does ethane have?

7

8

What is the name given to the hybrid orbitals found in ethane and ethene?

sp3 and sp2

9

What is a substitution reaction?

When an atom or a group of atoms in molecule is replaced by another atom or group of atoms.

10

During the Initiation step, what does the ultra violet light do?

It provides the energy required to break the chlorine-chlorine bond and to split some of the chlorine molecules into atoms.

11

What does a dot represent?

An unpaired electron

12

What type of fission takes place between the chlorine atoms?

Homolytic

13

When does homolytic fission occur?

When there is little or no polarity in the bond

14

What are radicals?

Atoms or groups of atoms with unpaired electrons

15

Desrcribe radicals

extremely unstable and therefore highly reactive

16

What is the initiation step in the chain reaction?

The process whereby radicals are generated

17

During the propagation step, what reactions occur?

CH4 + Cl. --> CH3. + HCl
CH3. + Cl2 ---> Ch3Cl + Cl.

18

What happens during the termination steps?

The number of radicals builds up, collisions between them occur and stable molecules are produced.

19

What is unique about the termination reactions

Radicals are used up and not regenerated. Such reactions bring the chain reaction to an end.