Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Unit
Principles of Chemistry
991 practice questions
Topics covered
- States of Matter102 practice questions
- Elements, Compounds and Mixtures69 practice questions
- Atomic Structure108 practice questions
- The Periodic Table103 practice questions
- Chemical Formulae, Equations and Calculations Part 119 practice questions
- Chemical Formulae, Equations and Calculations Part 2144 practice questions
- Ionic Bonding143 practice questions
- Covalent Bonding68 practice questions
- Metallic Bonding19 practice questions
- Electrolysis198 practice questions
Practice questions
111–120 of 161 · Hard
Question 111
8 marks · Hard
Answer and see the solution →Sodium chloride and magnesium oxide are both ionic compounds with giant ionic lattice structures.
(a)[4 marks]Describe, in terms of ions, the arrangement and structure of sodium chloride.
(b)[4 marks]Magnesium oxide, like sodium chloride, forms a giant ionic lattice, but in magnesium oxide every magnesium ion is Mg^{2+} and every oxide ion is O^{2-}. Magnesium oxide has a higher melting point than sodium chloride. Using your answer to part (a), explain why magnesium oxide has a higher melting point than sodium chloride.
Question 112
2 marks · Hard
Answer and see the solution →State what holds the atoms together in a covalent bond, and explain why a covalent bond only forms between certain atoms.
Question 113
5 marks · Hard
Answer and see the solution →Boron trifluoride (BF) is a covalent compound. Answer the following questions about its bonding.
(a)[1 mark]How many electrons are in the outer shell of a boron atom and of a fluorine atom?
(b)[2 marks]Draw a dot-and-cross diagram to show the covalent bonding in a molecule of BF. Use dots (•) for boron’s electrons and crosses (×) for fluorine’s electrons.
(c)[2 marks]Explain, using your diagram, why the central boron atom in BF does not have a full octet in its outer shell.
Question 114
2 marks · Hard
Answer and see the solution →Explain what a covalent bond is and describe how the sharing of electrons holds the bonded atoms together.
Question 115
2 marks · Hard
Answer and see the solution →Explain, using ideas about bonds and forces, why melting a substance with a simple molecular structure requires much less energy than melting a giant covalent structure such as diamond.
Question 116
5 marks · Hard
Answer and see the solution →The table shows data for three simple molecular substances:
Substance Relative molecular mass (Mr) Melting point (°C) Boiling point (°C) Electrical conductivity A 32 -210 -183 does not conduct B 44 -56 -1 does not conduct C 160 -7 59 does not conduct (a)[2 marks]Describe the trend shown by the melting points and boiling points as the relative molecular mass increases.
(b)[2 marks]Substance C is liquid at room temperature (25°C). Explain why substance C is a liquid at this temperature but substance A is a gas.
(c)[1 mark]Explain why none of these substances conduct electricity in any state.
Question 117
2 marks · Hard
Answer and see the solution →State one property that distinguishes a simple molecular structure from a giant covalent structure. Explain how this property relates to the forces present in each structure.
Question 118
2 marks · Hard
Answer and see the solution →Diamond is used for industrial cutting tools, while graphite is used as a lubricant. Explain, in terms of structure and bonding, why graphite can be used as a lubricant but diamond cannot.
Question 119
5 marks · Hard
Answer and see the solution →The three allotropes of carbon—diamond, graphite, and C60 fullerene—have different abilities to conduct electricity.
(a)[1 mark]State which, if any, of these allotropes can conduct electricity.
(b)[4 marks]For each allotrope, explain your answer by referring to their bonding and the movement of electrons.
Question 120
2 marks · Hard
Answer and see the solution →Describe the structure and bonding in C60 fullerene, referring to how carbon atoms are arranged and bonded in this allotrope.