Electronegativity and bond polarityEdexcel International A Level Chemistry: Subtopic test

1. 1
   Pauling electronegativity values: H 2.20, C 2.55, Cl 3.16, F 3.98 and Na 0.93.

   (a)

   Which bond is the most polar?

   [1 mark]

   • AC–H
   • BC–Cl
   • CC–F
   • DH–Cl

   (b)

   Which statement describes the polarity of the C–Cl bond?

   [1 mark]

   • AThe carbon atom has a partial positive charge and the chlorine atom a partial negative charge.
   • BThe carbon atom has a partial negative charge and the chlorine atom a partial positive charge.
   • CThe bond is non-polar because both atoms are non-metals.
   • DAn electron has been completely transferred, forming C⁺ and Cl⁻ ions.

   (c)

   Explain, using the data, why sodium chloride is ionic whereas hydrogen chloride is polar covalent.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   Pauling electronegativity values: H 2.20, C 2.55, O 3.44 and Cl 3.16. Carbon dioxide is a linear molecule (O=C=O), water is a bent (V-shaped) molecule, and chloromethane, CH₃Cl, methane, CH₄, and tetrachloromethane, CCl₄, are all tetrahedral.

   (a)

   Which statement about carbon dioxide is correct?

   [1 mark]

   • AIt is a polar molecule because the C=O bonds are polar.
   • BIt is a non-polar molecule because the C=O bonds are non-polar.
   • CIt is a polar molecule because it is linear.
   • DIt is a non-polar molecule even though the C=O bonds are polar, because the dipoles cancel.

   (b)

   Which molecule is polar?

   [1 mark]

   • ACCl₄
   • BCH₃Cl
   • CCO₂
   • DCH₄

   (c)

   Explain why water is a polar molecule.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   Pauling electronegativity values: H 2.20, F 3.98, Cl 3.16, I 2.66, Na 0.93 and Si 1.90.

   (a)

   Calculate the electronegativity difference in H–F, H–Cl and H–I. State which bond is the most polar and the direction of the dipole in that bond.

   [3 marks]

   (b)

   Use the data to explain how the bonding in sodium chloride differs from that in silicon tetrachloride, SiCl₄, and what this shows about ionic and covalent bonding.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   Pauling electronegativity values: H 2.20, B 2.04, C 2.55, N 3.04, F 3.98 and Cl 3.16. The molecules CCl₄ and CHCl₃ are tetrahedral, BF₃ is trigonal planar, and NH₃ is trigonal pyramidal with a lone pair on the nitrogen atom.

   (a)

   Define electronegativity, and explain why CCl₄ is a non-polar molecule but CHCl₃ is a polar molecule.

   [6 marks]

   (b)

   Compare the polarity of the bonds in BF₃ and NH₃ and predict, with reasons, whether each molecule is polar.

   [6 marks]

   Total for question 4: 12 marks

End of questions