Intermediate Bonding, Polarity, Intermolecular Forces and Solubility

Question 1

What does electronegativity measure?

Answer 1

The ability of an atom to attract an electron pair to itself in a covalent bond.

Question 2

What is caused if the difference between electronegativity of atoms in a molecule are high?

Answer 2

A dipole

Question 3

What does the bond polarity of a compound tell us?

Answer 3

The reactivity of a particular compound

Question 4

What are intermolecular forces?

Answer 4

The forces between MOLECULES

Question 5

What are the three main types of intermolecular forces?

Answer 5

1. London forces
2. Permanent dipole-dipole
3. Hydrogen bonds

Question 6

What are London forces caused by?

Answer 6

Instantaneous electron distribution in an atom, which results in a temporary dipole

Question 7

What does a temporary dipole cause?

Answer 7

An induced dipole in the opposite direction on a neighbouring atom

Question 8

What does the instantaneous electron distribution in an atom result in?

Answer 8

Weak attractive forces

Question 9

What results in greater London forces?

Answer 9

More electrons, which result in a greater induced dipole, which results in larger London forces

Question 10

What are permanent dipole-dipole forces caused by?

Answer 10

Difference in electronegativity

Question 11

What is Hydrogen bonding?

Answer 11

The attraction between Hydrogen in a polar bond and non-bonding electron on a nearby small electronegative ion

Question 12

What are the three atoms that H can bond to that will result in Hydrogen bonding?

Answer 12

Fluorine, Oxygen, Nitrogen (FON)

Question 13

How strong is Hydrogen bonding in comparison to London forces?

Answer 13

Hydrogen bonding results in a greater attraction between atoms in comparison to London forces.

Question 14

Why does boiling temperature increase as an alkane chain length increases?

Answer 14

The molecules are larger, so the London forces are greater

Question 15

Why are London forces greater in a straight chain, than they would be in a branched chain?

Answer 15

• Chains can line up
• Larger surface area
• Force is maximised

Question 16

Why do alcohols have higher boiling points than alkanes with the same number of electrons?

Answer 16

The H-O bond allows them to form Hydrogen bonds

Question 17

Why is fluorine an exception to the idea of increasing boiling points going down the halide group?

Answer 17

• Fluorine has fewest electrons
• But has much higher boiling point
• Able to form Hydrogen bonds (FON)

Question 18

Under what condition does a solution form?

Answer 18

A solution forms when one substance is dispersed uniformly throughout another

Question 19

Which points should you mention when comparing the solubility of liquids?

Answer 19

1. The intermolecular forces of EACH liquid

2. New potential intermolecular forces forming between 2 substances

Question 20

Why might two liquids not mix together?

Answer 20

• One may have stronger forces of attraction than the other
• Energy given out when new attraction forms is not sufficient to overcome the energy required to break the existing forces

Question 21

The energy required to overcome strong electrostatic forces of attractions in an ionic lattice is supplied by what?

Answer 21

The energy released when polar water molecules are attracted to the ions

Question 22

What is meant by the term ‘hydration energy’?

Answer 22

The energy released when ions are hydrated due to them being surrounded by water molecules

Question 23

What are the characteristics of the more electronegative elements?

Answer 23

Higher nuclear charges as there are more protons in the nucleus and similar atomic radii

Question 24

What is the pattern for increasing electronegativity in terms of the periodic table?

Answer 24

Across the periods and up the groups