Chemical Bonding

Q1. Potassium chloride and tetrachloromethane (CCl₄) are both compounds that contain chlorine. [Total: 10 marks]

(a) Draw a dot-and-cross diagram of potassium chloride. Show only the valence electrons. [2]

(b) Draw a dot-and-cross diagram of tetrachloromethane. Show only the valence electrons. [2]

(c) Potassium chloride and tetrachloromethane have different electrical conductivities.

(i) State the difference in electrical conductivity of the two compounds. [2]

(ii) With reference to its structure and bonding, explain the electrical conductivity of tetrachloromethane in part (c)(i). [2]

(iii) With reference to its structure and bonding, explain the electrical conductivity of potassium chloride in the solid state. [2]

Q2. Covalent compounds [Total: 5 marks]

(a) Draw and label dot-and-cross diagrams of ammonia and urea CO(NH₂)₂ using the key provided below. Show only the valence electrons. [3]

(b) Suggest a similarity and a difference in the physical properties of ammonia and urea. [2]

Similarity:

Difference:

Q3. Metallic structure [Total: 9 marks]

(a) With reference to its structure and bonding, explain why zinc is a suitable material to be used in a battery. Sketch a labelled diagram to support your answer. [4]

(b) With reference to its structure and bonding, explain why graphite is a suitable material to be used in a battery. [2]

(c) The Mohs scale, ranging from 1 to 10, is used to compare the hardness of different substances based on their ability to scratch each other. A harder material will have a higher number on the Mohs scale. For example, diamond has a hardness of 10.

(i) Predict the hardness of graphite on the Mohs scale. [1]

(ii) Explain your answer in part (c)(i). [2]

Q4. Diamond and buckminsterfullerene (C₆₀) are two different allotropes of carbon. Diamond has an extremely high melting point of over 3500 degree Celcius, whereas buckminsterfullerene (C₆₀) sublimes/melts at a significantly lower temperature of around 600 degree Celcius. [Total: 5 marks]

(a) Based on the information provided, state two differences between the structures of diamond and buckminsterfullerene. [2]

(b) Explain the difference in melting points based on their structure and bonding. [3]