MODULE 2: Shapes of Molecules and Intermolecular Forces

Question 1

How many degrees does the bond angle in a covalent bond decrease per lone pair of electrons?

Answer 1

2.5 degrees

Question 2

What is the bond angle in a covalent bond with 4 bonded pairs?

Answer 2

109.5 degrees

Question 3

What is the bond angle in a covalent bond with 3 bonded pairs and 1 lone pair?

Answer 3

107 degrees

Question 4

What is the bond angle in a covalent bond with 2 bonded pairs and 2 lone pairs?

Answer 4

104.5 degrees

Question 5

What is the bond angle in a covalent bond with just 3 bonded pairs and no lone pairs?

Answer 5

120 degrees

Question 6

What is the bond angle in a covalent bond with 6 bonded pairs and no lone pairs?

Answer 6

90 degrees

Question 7

What is the name of a covalent bond with 4 bonded pairs?

Answer 7

Tetrahedral

Question 8

What is the name of a covalent bond with 3 bonded pairs and 1 lone pairs?

Answer 8

Trigonal pyramidal

Question 9

What is the name of a covalent bond with 2 bonded pairs and 2 lone pairs?

Answer 9

Non-linear (because they’re bent!)

Question 10

What is the name of a covalent bond with 3 bonded pairs and no lone pairs?

Answer 10

Trigonal planar

Question 11

What is the name of a covalent bond with 6 bonded pairs and no lone pairs?

Answer 11

Octahedral

Question 12

Why do lone pairs cause more repulsion?

Answer 12

Because they are not shared, therefore have a more concentrated negative charge

Question 13

When drawing 3D molecules, what does a solid line represent?

Answer 13

A bond on the same plane as the paper

Question 14

When drawing 3D molecules, what does a solid wedge represent?

Answer 14

A bond that comes forward from the plane of the paper (towards you)

Question 15

When drawing 3D molecules, what does a dotted wedge represent?

Answer 15

A bond that goes away from the plane of the paper (away from you)

Question 16

What is electronegativity?

Answer 16

The ability of an atom in a covalent bond to attract the bonded pair of electrons

Question 17

How does electronegativity increase across the periodic table?

Answer 17

Up and to the right (towards fluorine)

Question 18

How is electronegativity measured?

Answer 18

Pauling electronegativity scale (0.0-4.0)

Question 19

What is a polar bond?

Answer 19

A bond where the shared pair of electrons is unequally distributed as the atoms sharing the bonds have different electronegativity values

Question 20

What is a non-polar bond?

Answer 20

A bond where the shared pair of electrons is shared equally between atoms

Question 21

What happens to the atoms with a polar bond?

Answer 21

They gain partial charges

Question 22

What symbol is used to represent partial charges?

Answer 22

Delta (δ)

Question 23

What are the partial charges in a polar bond called?

Answer 23

Permanent dipoles

Question 24

What are the different types of intermolecular forces?

Answer 24

London forces, permanent dipole-dipole interactions, hydrogen bonding

Question 25

What are London forces?

Answer 25

Weak intermolecular forces that exist between all molecules, occur due to movement of electrons around the nucleus (temporary)

Question 26

How does the strength of London forces change?

Answer 26

Increases as number of electrons increases

Question 27

What are simple molecular substances?

Answer 27

A substance made up of simple molecules (diatonic molecules) and only have London forces (H2, I2, etc)

Question 28

What are the properties of simple molecular substances?

Answer 28

Low melting and boiling points, no conductive

Question 29

What is the solubility of non-polar simple molecular substances?

Answer 29

Soluble in non-polar solvents, (tend to be) insoluble in polar solvents

Question 30

What is the solubility of polar simple molecular substances?

Answer 30

May dissolve in polar solvents, solubility depends on strength of dipole (stronger dipole = more soluble)

Question 31

What is a hydrogen bond?

Answer 31

A form of permanent dipole-dipole interaction that involves an electronegative atom with a lone pair of electrons (oxygen, nitrogen, fluorine) and a hydrogen attached to an electronegative atom with a lone pair of electrons

Question 32

How are hydrogen bonds represented in diagrams?

Answer 32

Dashed lines

Question 33

What are the anomalous properties of water?

Answer 33

Solid is less dense than liquid form, has a relatively high melting and boiling point

Question 34

Why is water less dense as a solid (ice)?

Answer 34

Hydrogen bonds hold water molecules in a lattice structure, so therefore the water molecules are 'pushed' further apart and ice expands, increasing the volume but maintaining the same mass (density is mass/volume). This causes ice to float)

Question 35

Why does water have a relatively high melting/boiling point?

Answer 35

Because of the stronger hydrogen bonds require more energy to break