COVALENT BONDING – IB1

1.       (i)      Draw the Lewis structures for carbon monoxide, carbon dioxide and the carbonate ion.

ANSWER

(3)

 

(ii)      Identify the species with the longest carbon-oxygen bond and explain your answer.

ANSWER

(3)

(Total 6 marks)

 

 

2.       How many lone pairs and bonding pairs of electrons surround xenon in the XeF₄ molecule?

	Lone pairs	Bonding pairs
A.	4	8
B.	0	8
C.	0	4
D.	2	4

ANSWER

(Total 1 mark)

 

 

3.       Identify the strongest type of intermolecular force in each of the following compounds.

CH₃Cl

CH₄

CH₃OH

ANSWER

(Total 3 marks)

 

 

4.       (i)      List the following substances in order of increasing boiling point (lowest first).

CH₃CHO              C₂H₆            CH₃COOH                  C₂H₅OH

ANSWER

(2)

(ii)      State whether each compound is polar or non-polar, and explain the order of boiling points in (i).

ANSWER

(8)

(Total 10 marks)

 

 

5.       Why is the boiling point of PH₃ lower than that of NH₃?

A.      PH₃ is non-polar whereas NH₃ is polar.

B.      PH₃ is not hydrogen bonded whereas NH₃ is hydrogen bonded.

C.      Van der Waals’ forces are weaker in PH₃ than in NH₃.

D.      The molar mass of PH₃ is greater than that of NH₃.

ANSWER

(Total 1 mark)

 

 

6.       Three scientists shared the Chemistry Nobel Prize in 1996 for the discovery of fullerenes.
Fullerenes, like diamond and graphite, are allotropes of the element carbon.

(i)      State the structures of and the bonding in diamond and graphite.

ANSWER

(2)

 

(ii)      Compare and explain the hardness and electrical conductivity of diamond and graphite.

ANSWER

(4)

 

(iii)     Predict and explain how the hardness and electrical conductivity of C₆₀ fullerene would compare with that of diamond and graphite.

ANSWER

(4)

(Total 10 marks)

 

 

7.       When the following bond types are listed in decreasing order of strength (strongest first), what is the correct order?

A.      covalent > hydrogen > van der Waals’

B.      covalent > van der Waals’ > hydrogen

C.      hydrogen > covalent > van der Waals’

D.      van der Waals’ > hydrogen > covalent

ANSWER

(Total 1 mark)

 

 

8.       Which fluoride is the most ionic?

A.      NaF

B.      CsF

C.      MgF₂

D.      BaF₂

ANSWER

(Total 1 mark)

 

 

9.       Which statement is true for compounds containing only covalent bonds?

A.      They are held together by electrostatic forces of attraction between oppositely charged ions.

B.      They are made up of metal elements only.

C.      They are made up of a metal from the far left of the periodic table and a non-metal from the far right of the periodic table.

D.      They are made up of non-metal elements only.

ANSWER

(Total 1 mark)

 

 

10.     Diamond, graphite and C₆₀ fullerene are three allotropes of carbon.

(i)      Describe the structure of each allotrope.

(3)

(ii)      Compare the bonding in diamond and graphite.

(2)

ANSWER

(Total 5 marks)

 

 

11.     Predict and explain which of the following compounds consist of molecules:
NaCl, BF₃, CaCl₂, N₂O, P₄O₆, FeS and CBr₄.

ANSWER

(Total 2 marks)