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
301–310 of 423 · Normal
Question 301
4 marks · Normal
Answer and see the solution →(a)[2 marks]Draw a dot-and-cross diagram to show the covalent bonding in an oxygen (O) molecule.
(b)[2 marks]Explain why there are two covalent bonds between the two oxygen atoms.
Question 302
3 marks · Normal
Answer and see the solution →A molecule of ammonia () is formed by nitrogen bonding covalently with three hydrogen atoms.
Given that each covalent bond is formed by the sharing of one pair of electrons, calculate the total number of electrons that nitrogen shares with hydrogen in ammonia.
Question 303
2 marks · Normal
Answer and see the solution →State two characteristic physical properties of substances with simple molecular structures and explain why they have these properties.
Question 304
4 marks · Normal
Answer and see the solution →The table shows the relative molecular mass and boiling points for two gaseous substances:
Gases and their boiling points Substance Relative molecular mass (Mr) Boiling point (°C) Methane 16 –161 Sulfur hexafluoride 146 –64 (a)[2 marks]Explain why both methane and sulfur hexafluoride are gases at room temperature despite having different molecular masses.
(b)[2 marks]Explain how increasing the molecular mass affects the boiling point of simple molecular substances, using these examples.
Question 305
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 306
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 307
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 308
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 309
2 marks · Normal
Answer and see the solution →Explain why substances with simple molecular structures do not conduct electricity, even when melted.
Question 310
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.