OZ.6

Question 1

In what way are the chemical properties of alkanes changed by the addition of halogen?

Answer 1

They become more reactive.

Question 2

What about the carbon-halogen bond in halogenoalkanes determines the difference in properties to normal alkanes?

Answer 2

The carbon halogen bond is polar.

Question 3

What results in polar bonds?

Answer 3

When atoms attract bonding electrons unequally, and one atom has a slightly negative charge as it gets a greater share of the bonding electrons, and the other slightly more positive.

Question 4

How is bond polarity represented?

Answer 4

δ+ - δ-

Question 5

Are all bonds polar and what does bond polarity depend on?

Answer 5

No, it depends on the electronegativity of atoms involved.

Question 6

What is electronegativity?

Answer 6

A measure of an atom’s tendency to attract electrons towards itself in a chemical bond.

Question 7

When are bonds non polar?

Answer 7

When there’s no difference in electronegativity of the atoms, generally when atoms are of the same element.

Question 8

When difference in electronegativity is small, what type of bond is formed?

Answer 8

Polar covalent bond.

Question 9

When difference in electronegativity is big, what type of bond is formed?

Answer 9

Ionic bond.

Question 10

Although halogenoalkanes contain polar bonds, some properties are still similar to alkanes. Are halogenoalkanes immiscible with water?

Answer 10

Yes, all halogenoalkanes are immiscible with water like alkanes, meaning do not mix.

Question 11

What does the boiling points of halogenoalkanes depend on?

Answer 11

Depends on the halogen present and number of halogen atoms present. The bigger the halogen atom and the more halogens there are, the higher the boiling point.

Question 12

What bond is broken when solid melts or liquid boils?

Answer 12

The intermolecular bonds.

Question 13

What are intermolecular bonds?

Answer 13

The bonds that hold molecules together in liquids and solids.

Question 14

Are bonds within molecules broken when substance is boiled or melted?

Answer 14

No.

Question 15

What is the trend for the intermolecular forces of alkanes?

Answer 15

The longer the alkane chain, the stronger the intermolecular forces, which therefore means the higher the boiling points.

Question 16

How does the boiling points vary with straight chain alkanes and their branched isomers?

Answer 16

Straight chain alkanes allow more contact between molecules and therefore stronger intermolecular forces, therefore higher boiling points than their branched isomers.

Question 17

What is a dipole?

Answer 17

A dipole is a molecule/part of a molecule, with a positive end and a negative end, as a result of its polar bonds.

Question 18

What is a molecule said to be if it has a dipole?

Answer 18

It is polarized.

Question 19

What are three types of dipole in which molecules can become polarized with?

Answer 19

• Permanent dipole
• Instantaneous dipole
• Induced dipole

Question 20

When does a permanent dipole occur?

Answer 20

When there is a polar bond in the molecule as a result of the difference in electronegativity of two atoms. This means that one end of the bond will be more negative and attract electrons more compare to the other end.

Question 21

Does a molecule that contains polar bonds have to be a polar molecule?

Answer 21

No, if polar bonds are exerted on opposing directions, the polarity will cancel out, meaning that is the molecule is non polar overall.

Question 22

When does a instantaneous dipole occur?

Answer 22

When there is a temporary difference in negative charges on either ends of the molecule due to constant movements of electrons, making one end slightly more negative than the other at that instance.

Question 23

When does a induced dipole occur?

Answer 23

When an unpolarized molecule is next to a dipole, to which the dipole attracts or repels the electrons in the unpolarized molecule, inducing a dipole in it..

Question 24

Attractions between dipoles give rise to what type of bonds?

Answer 24

Intermolecular bonds.

Question 25

What are three types of dipole intermolecular bonds?

Answer 25

1. Instantaneous dipole - induced dipole (Id-Id)
2. Permanent dipole - permanent dipole (Pd-Pd)
3. Permanent dipole - induced dipole (Pd-Id)

Question 26

Which type of intermolecular bonding is the weakest?

Answer 26

Instantaneous dipole - induced dipole.

Question 27

What are two factors that affects the effects of id-id intermolecular forces?

Answer 27

1. The more electrons the atoms have, the stronger the effect.
2. The more branching the molecules have, the weaker the effect.

Question 28

Which type of intermolecular force exists between all molecules?

Answer 28

Instantaneous dipole - induced dipole.