Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Section
Simple molecular structures
19 practice questions
Practice questions
11–19 of 19
Question 11
3 marks · Normal
Answer and see the solution →Hexane is a simple molecular compound. It melts at –95°C and boils at 69°C. Calculate the temperature range (in °C) over which hexane is a liquid and explain why this range exists for simple molecular substances.
Question 12
3 marks · Normal
Answer and see the solution →Explain why bromine (Br2) is a liquid at room temperature, whereas chlorine (Cl2) is a gas, in terms of molecular mass and intermolecular forces.
Question 13
4 marks · Normal
Answer and see the solution →Analyze the data in the table below and answer the questions.
Melting and boiling points of halogens Halogen Formula Relative molecular mass (Mr) Melting point (°C) Boiling point (°C) Fluorine F2 38 –220 –188 Chlorine Cl2 71 –101 –34 Bromine Br2 160 –7 59 Iodine I2 254 114 184 (a)[1 mark]Describe the trend in boiling points as you go down the group from fluorine to iodine.
(b)[2 marks]Explain this trend in terms of molecular structure and forces.
(c)[1 mark]Which halogen is a solid at room temperature (25°C)? Explain how you decided.
Question 14
1 mark · Normal
Answer and check →Which statement describes the effect of increasing molecular mass on the boiling point of simple molecular substances?
- A.Boiling point decreases as molecular mass increases.
- B.Boiling point stays the same as molecular mass increases.
- C.Boiling point increases as molecular mass increases.
- D.Boiling point alternates up and down as molecular mass increases.
Question 15
2 marks · Normal
Answer and see the solution →Explain why substances with simple molecular structures do not conduct electricity, even when melted.
Question 16
4 marks · Normal
Answer and see the solution →A student compares the properties of diamond (a giant covalent structure) with carbon dioxide (a simple molecular compound).
(a)[1 mark]State one difference between the melting points of diamond and carbon dioxide.
(b)[2 marks]Explain this difference in terms of bonding and structure.
(c)[1 mark]Which of the two substances can conduct electricity? Explain your answer.
Question 17
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 18
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 19
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.