Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Chapter
Covalent Bonding
68 practice questions
Topics covered
Practice questions
21–30 of 68
Question 21
3 marks · Easy
Answer and see the solution →The table shows properties of two substances, X and Y.
Properties of X and Y Substance Relative molecular mass (Mr) Physical state at room temp. Electrical conductivity X 32 gas does not conduct Y 160 liquid does not conduct (a)[2 marks]Which substance, X or Y, has the higher boiling point? Explain your answer.
(b)[1 mark]Suggest why neither substance conducts electricity.
Question 22
2 marks · Easy
Answer and see the solution →Iodine melts at 114°C and boils at 184°C. Calculate the temperature range (in °C) over which iodine is a liquid.
Question 23
2 marks · Easy
Answer and see the solution →Explain why methane (CH₄) has a much lower boiling point than water (H₂O), using ideas about molecular mass and intermolecular forces.
Question 24
3 marks · Easy
Answer and see the solution →Examine the table below showing properties of some substances.
Properties of Substances Substance Structure Melting point (°C) Boiling point (°C) Oxygen simple molecular -219 -183 Graphite giant covalent 3930 4830 Sulphur dioxide simple molecular -73 -10 (a)[1 mark]Which substance in the table is likely to have the hardest structure? Give a reason.
(b)[2 marks]Explain why oxygen has a much lower melting point than graphite.
Question 25
1 mark · Easy
Answer and see the solution →State what happens to the boiling point of chlorine (Cl₂) as its relative molecular mass increases.
Question 26
3 marks · Easy
Answer and see the solution →Describe the structure and properties of a substance with a simple molecular structure.
(a)[1 mark]State the type of bonds within a simple molecule.
(b)[1 mark]Describe the forces between the molecules.
(c)[1 mark]Explain why these substances have low melting and boiling points.
Question 27
2 marks · Easy
Answer and see the solution →The melting point of fluorine is –220°C and its boiling point is –188°C. Calculate how many degrees fluorine is a liquid.
Question 28
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 29
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 30
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.