Module 2 Chapter 6 -shape Of Molecules And Forces

Question 1

Predict the shape of a molecule of SbCl3.

Explain your answer

Answer 1

Pyramidal

Because SbCl3 has 3 bonding pairs and one lone pair of electrons. The pair of electrons repel.

Question 2

SbCl3 molecules are polar.

Explain your answer.

Answer 2

There is a difference in electronegativities between Sb and Cl.
The molecule is not symmetrical and the dipoles do not cancel

Question 3

State and explain two anomalous properties of ice caused by hydrogen bonding.

Answer 3

1. Ice is less dense than water because the molecules in ice are held together by hydrogen bonds.
2. Ice has a relatively high melting point because hydrogen bonds are stronger and more energy is required to break the bonds.

Question 4

Explain what is meant by the term electronegativity

Answer 4

Electronegativity is the ability of an atom to attract the pair of electrons in a covalent bond

Question 5

Explain why CH2Cl2 molecule is polar

Answer 5

The molecule is non symmetrical and the dipoles do not cancel out

Question 6

Predict the shape and bond angle in a molecule that has 2 bonding pairs and 2 lone pairs around a central atom.

Answer 6

Non linear - 104.5°

Question 7

Suggest the shape of the F2O molecule and the bond angle

Answer 7

Non linear

104.5°

Question 8

What is the oxidation number of oxygen in F2O?

Answer 8

2+

Question 9

Describe how london forces arise

Answer 9

Both atoms have an even distribution of electrons,
for the fraction of time there is an uneven distribution of electrons which creates an instantaneous dipole
Meaning the neighbouring molecule produces an induced dipole

Question 10

Suggest why there are no other intermolecular forces in solid sulfur

Answer 10

There’s only one atom - no permanent dipole

Question 11

State and explain the trend in the boiling points of chlorine, bromine and iodine.
Use ideas of london forces

Answer 11

As you go down the group, the boiling point increases because there is a greater number of electrons and stronger london forces therefore more energy is needed to break the london forces.

Question 12

Which substances experiences induced dipole dipole interactions (London forces)?

1. C2H5OH
2. H2O
3. SiO2

Answer 12

Only 1 and 2

Question 13

What happens to the trend in boiling points down the halogen group?

Answer 13

The induced dipole-dipole interactions(London Forces) increases

Question 14

Magnesium and silicon have different types of giant structures.
Describe the bonding in magnesium and in silicon.
Include the names of the particles and describe the forces between the particles in the structure.

Answer 14

Magnesium is a metallic bond and they have delocalised electrons to be able to conduct electricity.
Silicon is a covalent bond and occurs between atoms

Question 14

Magnesium and silicon have different types of giant structures.
Describe the bonding in magnesium and in silicon.
Include the names of the particles and describe the forces between the particles in the structure.

Answer 14

Magnesium is a metallic bond and they have delocalised electrons to be able to conduct electricity.
Silicon is a covalent bond and occurs between atoms

Question 15

At room temperature and pressure, the first 4 members of the alkanes are all gases but the first four alcohols are all liquids.
Explain this difference in terms of intermolecular forces.

Answer 15

Alcohols have hydrogen bonds and London forces

Hydrogen bonds are the strongest bond out of the three, and alkanes only have London forces.

Question 16

Explain why a CF4 molecule has polar bonds but does not have an overall dipole.

Answer 16

F is more electronegative than C

CF4 is symmetrical as it forms a tetrahedral shape therefore there is no overall dipole

Question 17

The boiling point of butan-1-ol is 118 degrees. The boiling point of 2-methypropan-2-ol is 82 degrees. Why is the boiling point of butan-1-ol higher than that of 2-methylpropan-2-ol?

Answer 17

Butan-1-ol has stronger induced dipole-dipole interactions because it has a straight chain structure

Question 18

Explain what is meant by the term electronegativity and suggest why SF6 molecules are non polar.

Answer 18

The ability of an atom to attract electrons in a covalent bond. Because SF6 is a symmetrical shape

Question 19

State and explain the trend in the boiling points of chlorine, bromine and iodine.

Answer 19

As you go down the group the boiling point increases because there is a greater number of electrons and stronger London forces therefore more energy is needed to break the London forces.

Question 20

What is the shape name and bond angle of a shape that has 4BP and 0LP

Answer 20

Tetrahedral

109.5 degrees

Question 21

What is the shape name and bond angle of a shape that has 3BP and 1LP

Answer 21

Trigonal Pyramidal

107

Question 22

What is the shape name and bond angle of a shape that has 2 BP and 2LP

Answer 22

Bent/Non linear

104.5

Question 23

What is the shape name and bond angle of a shape that has 3BP and 0LP

Answer 23

trigonal planar

120 degrees

Question 24

What is the shape name and bond angle of a shape that has 2BP and 0LP

Answer 24

Linear

180

Question 25

What is the shape name and bond angle of a shape that has 5BP and 0LP

Answer 25

trigonal bipyramidal

120/90

Question 26

What is the shape name and bond angle of a shape that has 6BP and 0LP

Answer 26

Octahedral

90

Question 27

What is the shape name and bond angle of a shape that has 2BP and 1LP

Answer 27

Bent/Non linear - <120

Question 28

State the shape and bond angle around a carbon atom in the alkyl group of propanoic acid .
Explain the shape

Answer 28

Tetrahedral
109°
Four bonded pairs repel