Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Chapter
Covalent Bonding
68 practice questions
Topics covered
Practice questions
21–28 of 28 · Normal
Question 21
4 marks · Normal
Answer and see the solution →The table shows the melting points and hardness for three forms of carbon.
Properties of carbon allotropes Allotrope Melting point/°C Hardness Diamond 3550 Very hard Graphite 3600 Soft C60 fullerene 280 Soft (a)[2 marks]Using only the data, identify which allotrope(s) have a giant covalent structure. Explain your reasoning.
(b)[2 marks]Using the data and your knowledge, explain why C60 fullerene has a lower melting point than graphite.
Question 22
1 mark · Normal
Answer and check →Which statement correctly compares the electrical conductivity of diamond, graphite, and C60 fullerene?
- A.Only graphite conducts electricity because it has delocalised electrons.
- B.Only diamond conducts electricity because it has a giant covalent structure.
- C.Diamond and C60 fullerene both conduct electricity, but graphite does not.
- D.All three conduct electricity equally well.
Question 23
2 marks · Normal
Answer and see the solution →Describe the bonding in diamond in terms of the arrangement of carbon atoms and the bonds formed.
Question 24
4 marks · Normal
Answer and see the solution →Diamond is a non-conductor of electricity and is very hard, while graphite is soft but conducts electricity.
(a)[2 marks]Explain, in terms of bonding and structure, why diamond does not conduct electricity.
(b)[2 marks]Explain, using bonding and the arrangement of atoms, why graphite is soft.
Question 25
6 marks · Normal
Answer and see the solution →This question is about covalent bonds and giant covalent structures.
(a)[2 marks]Define a covalent bond.
(b)[2 marks]Describe what holds the atoms together in a covalent bond.
(c)[2 marks]Diamond and graphite both contain carbon atoms joined by covalent bonds. State one way in which their structures are similar and one way in which they are different.
Question 26
6 marks · Normal
Answer and see the solution →This question is about the structures of covalent molecules and giant covalent substances.
(a)[2 marks]Draw a dot-and-cross diagram (showing only outer shell electrons) for a molecule of water (H2O).
(b)[2 marks]Diamond and graphite are giant covalent structures made only of carbon atoms.
i. State how many other carbon atoms each carbon is bonded to in:
• diamond
• graphite
(c)[2 marks]Explain, in terms of structure and bonding, why diamond has a much higher melting point than water.
Question 27
6 marks · Normal
Answer and see the solution →This question tests your understanding of covalent bonding and how it affects the properties of substances.
(a)[2 marks]Calculate the total number of covalent bonds formed in a molecule of ethene (C2H4). Show your working.
(b)[4 marks]The table shows the electrical conductivity of three substances:
Substance Electrical conductivity Diamond Does not conduct Graphite Conducts C60 fullerene Does not conduct Explain, using their structure and bonding, why graphite conducts electricity but diamond and C60 fullerene do not.
Question 28
6 marks · Normal
Answer and see the solution →This question is about using dot-and-cross diagrams to interpret structures and properties.
(a)[2 marks]Draw a dot-and-cross diagram for a molecule of nitrogen, N2, showing only the outer shell electrons.
(b)[2 marks]Explain why nitrogen gas contains molecules, not a giant covalent structure like diamond and graphite.
(c)[2 marks]Explain why simple covalent molecules like N2 have much lower melting points than giant covalent structures such as diamond.