Chapter 3.4 - Bonding And Physical Properties

Question 1

State the properties of graphite

Answer 1

• Slippery
• Can conduct electricity
• High mp
• Insoluble

Question 2

Explain why graphite is slippery

Answer 2

Weak bonds between the layers in graphite are easily broken, so the layers can slide over each other

Question 3

Explain why graphite is a good conductor of electricity

Answer 3

Graphite has delocalized electrons which carry charge

Question 4

Explain why graphite has a high mp

Answer 4

Because of the strong covalent bonds in the hexagon sheets graphite has a very high mp

Question 5

Why is graphite insoluble ?

Answer 5

The covalent bonds in the sheet are too strong to break

Question 6

Describe the bonds in diamond

Answer 6

Each carbon atom is covalently bonded to four other carbon atoms forming a tetrahedral shape

Question 7

State the properties of diamond

Answer 7

• high mp
• hard
• good thermal conductor
• can’t conduct electricity
• insoluble

Question 8

Explain In terms of its structure and bonding, why nickel conducts electricity

Answer 8

• metallic bond,

- strong attraction between positive ions and delocalized electrons

Question 9

Explain why CHF3 has a higher mp than CF4 (3)

Answer 9

CHF3 contains polar bonds,
There are permanent dipole ,

CF3 contains polar bonds but they cancel each other out due to the shape, there are van daar waals forces between them

Therefore CHF3 has strong intermolecular forces requiring more energy to break dowm

Question 10

Give the name of the type of crystal structure shown by silicon dioxide

Answer 10

Giant covalent structure

Question 11

Explain why silicon dioxide does not conduct electricity when molten

Answer 11

No delocalized electrons

Question 12

Deduce why the bonding in nitrogen oxide is covalent rather than ionic

Answer 12

Small electronegativity difference

Question 13

Suggest why graphene is an excellent conductor of electricity.

Answer 13

• It has Delocalized electrons,

- Able to move

Question 14

Explain, in terms of its structure and bonding, why graphene has a high melting point (2)

Answer 14

• Covalent bonds,

- Many /strong / hard to break / need a lot of energy to break

Question 15

Name the type of bonding in the element sodium

Answer 15

Metallic

Question 16

Suggest why titanium can be hammered into different shapes.

Answer 16

Layers can slide over each other

Question 17

Suggest why these objects with different shapes have similar strengths

Answer 17

Strong metallic bonding re-formed

Question 18

Explain, in terms of its structure and bonding, why titanium has a high melting point. (2)

Answer 18

• positive ions and delocalised electrons are attracted,

- strong attraction

Question 19

Magnesium oxide (MgO) has a melting point of 3125 K.
Predict the type of crystal structure in magnesium oxide and suggest why its melting point is high.
Type of crystal
Explanation

Answer 19

• giant ionic,

- strong attraction between oppositely charged ions

Question 20

Explain why the melting point of sodium chloride is high

Answer 20

• ionic bond,

- strong attraction between ions of opposite charges

Question 21

Explain in terms of bonding why KBrF has a high melting point

Answer 21

• ionic bond,

- strong forces of attraction between oppositely charged ions

Question 22

Explain, in terms of structure and bonding, why the melting point of carbon is high (3)

Answer 22

• macromolecular,
• covalent bonds in the structure,
• covalent bonds need a lot of energy to break

Question 23

Describe the bonding in a metal (2)

Answer 23

-positive ions attracted to delocalized electrons

Question 24

Explain each of these properties of diamond and graphite in terms of structure and
bonding. (6)

Answer 24

Diamond

• atoms in diamond joined to 4 other carbon atoms forming a tetrahedral shape
• diamond is hard and strong bcoz of its 3D shape,
• giant covalent structure

Graphite

• giant covalent structure
• atoms in graphite joined to 3 other carbon atoms forming a Trigonal planar shape,
• graphite is soft as layers can slide over each other

Question 25

Give one other difference in the properties of diamond and graphite.

Answer 25

diamond is non-conductor of electricity, graphite is conductor

Question 26

Why do diamond and graphite both have high melting points ?

Answer 26

- giant covalent structure | - strong covalent bonds

Question 27

Why is graphite a good conductor of electricity?

Answer 27

It has delocalized electrons

Question 28

Why is graphite soft ?

Answer 28

Layers can slide over each other

Question 29

Describe the bonding in a crystal of iodine (2)

Answer 29

- van der waals between molecules, | - covalent bonds between atoms

Question 30

In terms of its structure and bonding, suggest why graphite has a very high melting point (2)

Answer 30

- macromolecular | - strong covalent bonds

Question 31

State the type of structure present in each case and explain why the melting point of diamond is so high.

Answer 31

-diamond is a macromolecular | C-C bonds need to be broken which takes a lot of energy bcoz bonds are strong

Question 32

Describe the bonding in, and the structure of, sodium chloride and ice

Answer 32

- NaCl is ionic, - strong attraction between ions of opposite charge - covalent bonds between atoms in water - hydrogen bonding between water molecules - covalent bonds in ice are strong - tetrahedral

Question 33

Explain how the ions are held together in solid sodium metal

Answer 33

Strong attraction between positive ions and delocalized electrons

Question 34

Explain how the ions are held together in solid sodium chloride.

Answer 34

- ionic bond, | - strong attraction between ions of opposite charge

Question 35

Compare the electrical conductivity of solid sodium metal with that of solid sodium chloride. Explain your answer. Comparison, Explanation

Answer 35

- sodium conducts and NaCl doesn’t, - sodium has delocalized electrons that carry charge, - ions cannot move in NaCl but can when molten

Question 36

State the type of crystal structure for each of iodine and graphite.

Answer 36

Iodine- molecular , | Graphite- giant covalent/macromolecular

Question 37

Describe the structure of and bonding in graphite and explain why the melting point of graphite is very high.

Answer 37

- Layers of C-C bond connected by covalent bonds, - van der waals forces between layers, - strong covalent bonds need to be broken down

Question 38

Explain why iodine vaporises when heated gently

Answer 38

Van der waals forces between molecules are weak