F322-Alkanes

Question 0

What are alkanes?

Answer 0

A homologous series of compound with the same general formula

Question 1

Saturated

Answer 1

Organic compounds containing only single covalent bonds

Question 2

What is the general formula of an alkane

Answer 2

CnH(2n+2)

Question 3

What is the shape around the carbon atom in an alkane?

Answer 3

Tetrahedral

Question 4

What is the type of chemical bonding between carbon and hydrogen atoms?

Answer 4

Covalent bonds

Question 5

What is the bond angle in Alkanes?

Answer 5

109.5*

Question 6

Empirical formula

Answer 6

The simplest whole number ratio of atoms of each element present in a compound

Question 7

Molecular formula

Answer 7

The actual number of atoms of each element in a molecule

Question 8

Displayed formula

Answer 8

Shows every element and every bond in the structure

Question 9

Structural formula

Answer 9

The minimum detail required to show the arrangement of the atoms in a molecule

Question 10

Skeletal formula

Answer 10

Simplified organic formula with the H atoms( on the backbone) removed leaving the carbon skeleton

Question 11

Name the first 10 alkanes

Answer 11

Methane
Ethane
Propane
Butane
Pentane
Hexane
Heptane
Octane
Nonane
Decane

Question 12

Name the branch with 1 carbon in side chain

Answer 12

Methyl

Question 13

Name the branch with 2 carbons in side chain

Answer 13

Ethyl

Question 14

Name the branch with 3 carbons in side chain

Answer 14

Propyl

Question 15

Explain why the boiling point of alkanes increases when the chain length increases.

Answer 15

~As the chain length of alkanes increases the points of contact between molecules increases.
~There are more intermolecular van der Waals’ forces between molecules.
~More energy is needed to break the stronger intermolecular forces.

Question 16

Explain why hexane has a higher boiling point than 3-methylpentane.

Answer 16

~As the branching of alkanes increases, the points of contact between molecules decreases.
~Branched molecules cannot pack as closely together.
~There are weaker van der Waals’ forces between the molecules.
~Less energy is needed to break the weaker intermolecular forces.

Question 17

Give the general formula for a cyclic alkane.

Answer 17

CnH2n

Question 18

What needs to be present for radical substitution?

Answer 18

Ultraviolet radiation

Question 19

What does an alkane react with in radical substitution?

Answer 19

Chlorine or Bromine

Question 20

Radical

Answer 20

A species with an unpaired electron

Question 21

What is step 1 of radical substitution & what happens?

Answer 21

Initiation- UV radiation causes the covalent bond within the halogen molecule to break forming a radical. (Homolytic fission)

Question 22

Homolytic Fission

Answer 22

A type of covalent bond fission which forms two radicals

Question 23

Give an example of initiation in radical substitution.

Answer 23

Cl2 > 2Cl

Question 24

What happens in the first part of step 2 in radical substitution?

Answer 24

Propagation

The halide radical reacts with the alkane molecule to form an alkyl radical and HCl. (Cl+CH4 > CH3 + HCl*)

Question 25

What happens in the second part of Propagation? (Step 2 of radical substitution)

Answer 25

The alkyl radical reacts with a halogen molecule and this regenerates the halide radical. (CH3* + Cl2 > Cl* + CH3Cl*)

Question 26

What do the two parts of propagation result in?

Answer 26

They add together to result in the final equation of the reaction. (CH4 + Cl2 > CH3Cl + HCl)

Question 27

What is step 3 of Radical substitution?

Answer 27

Termination - two radicals combine to form a molecule. (Cl + Cl > Cl2) or (CH3 + CH3 > C2H6) or other

Question 28

What is a problem with radical substitution?

Answer 28

Further substitution can occur with the formation of a mixture of products