Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Chapter
Covalent Bonding
68 practice questions
Topics covered
Practice questions
61–68 of 68
Question 61
5 marks · Easy
Answer and see the solution →(a)[2 marks]Draw a dot-and-cross diagram to show the covalent bonding in a molecule of ammonia (NH).
(b)[2 marks]Explain why ammonia is a gas at room temperature, using your understanding of intermolecular forces.
(c)[1 mark]State how many lone pairs of electrons are present on the nitrogen atom in the ammonia molecule.
Question 62
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 63
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 64
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 65
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.
Question 66
8 marks · Hard
Answer and see the solution →This question is about the differences in properties between substances with simple molecular structures and those with giant covalent structures.
(a)[2 marks]Explain why substances with simple molecular structures, such as chlorine (Cl₂), have low melting and boiling points.
(b)[3 marks]Diamond and graphite are both forms of carbon, but diamond is much harder than graphite. Explain, in terms of structure and bonding, why diamond is harder than graphite.
(c)[3 marks]State and explain whether Cl₂ can conduct electricity. Then compare this with the ability of diamond to conduct electricity, explaining your reasoning.
Question 67
7 marks · Hard
Answer and see the solution →This question is about how the physical properties of substances are linked to their structures and electrical conductivity.
(a)[0 marks]The table shows data for some simple molecular and giant covalent substances:
Melting and boiling points of selected substances. Substance Relative molecular mass / Mr Melting point / °C Boiling point / °C Chlorine (Cl₂) 71 -101 -34 Bromine (Br₂) 160 -7 59 Iodine (I₂) 254 114 184 Diamond – 3550 4830 (b)[2 marks]Using data from the table, describe and explain how the melting and boiling points of the halogens change as the relative molecular mass increases.
(c)[2 marks]Explain why the melting point of diamond is much higher than those of the halogens listed, using ideas about structure and bonding.
(d)[3 marks]State whether graphite conducts electricity. Suggest, based on your knowledge of its structure, why this is different from diamond and the halogens.
Question 68
7 marks · Hard
Answer and see the solution →This question is about how the type of structure affects properties in covalent and giant covalent substances.
(a)[2 marks]Explain what is meant by a 'simple molecular structure', using water (H₂O) as an example.
(b)[3 marks]Compare the structure and bonding found in C₆₀ fullerene with that in graphite.
(c)[2 marks]State which would have a higher melting point, graphite or C₆₀ fullerene. Explain your answer in terms of their bonding and structures.