2. Bonding Click to start

3. Question 1 Which compound contains ionic bonds? Ethanoic acid, CH 3 COOH Dichloroethane, CH 2 Cl 2 Silicon tetrabromide,SiBr 4 Magnesium chloride, MgCl 2

4. Wrong Answer! Magnesium is a metal and chlorine is a non-metal. Typically, a metal and non-metal react to form an ionic compound.

5. NH 3, CH 4, H 2 O Question 2 When CH 4, NH 3 and H 2 O are arranged in order of dereasing bond angle, what is the correct order? CH 4, NH 3, H 2 O NH 3, H 2 O, CH 4 H 2 O, NH 3, CH 4

6. Wrong Answer! All the molecules are based upon tetrahedral arrangement of 4 regions of high electron density. However, lone pairs cause more repulsion than bonding pairs. The oxygen in H 2 O is surrounded by 2 lone pairs (max repulsion), the nitrogen atom in NH 3 contains 1 lone pair, but the carbon in CH 4 has no lone pairs ( least repulsion)

7. Question 3 In which of the following is there at least one double bond? I.O 2 II.CO 2 III.C 2 F 2 I only III only I, II and III II and III only

8. Wrong Answer! The oxygen molecule (O=O) contains 1 double bond, the carbon dioxide (O=C=O) contains 2 double bonds and thetetrafluoroethane molecule contains 1 double bond

9. Question 4 Why is the boiling point of ethane greater than that of neon? The ethane molecule is polar. Hydrogen bonds form between ethane molecules but not present in liquid neon. A molecule of ethane has a greater mass than a neon atom. More electrons are present in ethane than in neon.

10. Wrong Answer! Both ethane and neon are non-polar. Hence, the predominant intermolecular and inter-atomic forces are van der Waals’ forces whose size depends on the number of electrons present in the atoms or molecules. A greater number of electrons in the ethane molecule results in a stronger temporary dipole which makes neighbouring molecules or atoms attract each other more strongly. This means more heat is reqiured to overcome the intermolecular or inter-atomic forces in ethane molecules, resulting higher boiling point.

11. Question 5 What is the formula for the compound formed by strontium and nitrogen? Sr 3 N 2 Sr 2 N 3 SrN Sr 2 N

12. Wrong Answer! Strontium form Sr 2+ and nitrogen forms N 3-.Hence, the formula of strontium nitride is Sr 3 N 2

13. Question 6 A solid has a melting point 1440 0 C. It conducts heat and electricity. It does not dissolve in water or in organic solvents. The bond between the particle is most likely to be covalent ionic metallic dipole-dipole

14. Wrong Answer! Generally, metals have high melting points, contain delocalized electrons, insoluble in water and excellent conductors.

15. Question 7 Which is the best description of metallic bonding? The attraction between positve and negative ions. The attraction between the nuclei of positive ions and delocalized valene electrons. The attraction between nuclei and shared electron pairs. The attraction between protons and electrons.

16. Wrong Answer! D is a description of covalent bonding. A is a description of ionic bonding.

17. Question 8 Which compound is the most soluble in water? ethane propane hexan-1-ol propan-1-ol

18. Wrong Answer! Ethane and propane are hydrocarbons and hence unable to form hydrogen bonds with water. Propan-1-ol and hexan-1-ol are both alcohols and contan hydroxyl group –OH, capable of forming hydrogen bonds with water molecules. However, propan-1-ol is more soluble since its hydrocarbon chain is smaller, 3 C atoms compared to 6 in hexan-1-ol.

19. Question 9 Which is not present in C 2 H 5 OC 2 H 5 in the liquid state? covalent bonding van der Waals’ force hydrogen bonding dipole-dipole attractions

20. Wrong Answer! All of the hydrogen atoms are attached to C atoms and hence are unable to engage in hydrogen bonding.

21. Question 10 The angle between the two carbon-carbon bonds in CH 3 CHCF 2 is closest to 180 0 120 0 90 0 109 0

22. Wrong Answer! The molecule has a C=C bond. There are 3 regions of high electron density around the 2 carbon atoms. Hence, the molecule is trigonal planar and has bond angles of 120 0.

23. Question 11 The molar masses of C 2 H 6, CH 3 OH and CH 3 F are similar. How do their boiling points compare? C 2 H 6 <CH 3 OH<CH 3 F CH 3 F<CH 3 OH<C 2 H 6 C 2 H 6 <CH 3 F<CH 3 OH CH 3 OH<CH 3 F<C 2 H 6

24. Wrong Answer! Ethane, C 2 H 6 has a lower boiling point due to the presence of van der Waals forces of attraction – weakest of the 3 intermolecular forces. Fluoromethane, CH 3 F has an intermediate boiling point owing to the presence of dipole-dipole forces. Methanol, CH 3 OH has the highest boiling point owing to the presence of hydrogen bonding.

25. Question 12 Which of the following molecules is a triangular planar? NCl 3 C2H4C2H4 SF 6 C3H6C3H6

26. Wrong Answer! C 2 H 4 has a trigonal planar arrangement around the 2 carbon atoms.

27. Question 13 Which intermolecular forces exist in dry ice, CO 2 (s)? dipole-dipole interactions covalent bonds hydrogen bonds van der Waals’ forces

28. Wrong Answer! CO 2 is a non-polar molecule due to its linear shape. The 2 dipoles cancel each other out. Hence, the forces operating in the soild are van der Waals’ forces.

29. Question 14 In general, the strengths of the following intermolecular forces and bonds increase in the order covalent bonds, hydrogen bonds, van der Waals forces covalent bonds, van der Waals forces, hydrogen bonds hydrogen bonds, covalent bonds, van der Waals forces van der Waals forces hydrogen bonds, covalent bonds

30. Wrong Answer! The relative order of strength is van der Waals’ forces, hydrogen bonds, covalent bonds

31. Question 15 Given the following electronegativity values: H: 2.1N: 3.0O: 3.5F:4.0 which bond has the greatest polarity? O-H in H 2 O N-O in NO 2 N-H in NH 3 N-F in NF 3

32. Wrong Answer! The largest difference in electronegativity value is from O and H atoms.

33. Question 16 Which one of the species has a triangular pyramidal geometry? BCl 3 NCl 3 C2H3C2H3 H 2 Se

34. Wrong Answer! The nitrogen atom in NCl 3 is surrounded by 3 bonding pairs and 1 lone pair.

35. II and III only Question 17 In which of the following substances would hydrogen bonding be expected to occur? I.C 2 H 6 II.CH 3 CH 2 COOH III.CH 3 COCH 3 II only I and III only I, II and III

36. Wrong Answer! A hydrogen bond would expect to occur in CH 3 CH 2 COOH since it contains hydrogen bonded directly to oxygen. The OH group is able to engage in hydrogen bonding. In the other 2 compounds, the hydrogen is bonded to C.

37. Question 18 When the Lewis structure for HCOOCH 3 is drawn, how many bonds and how many lone pairs of electrons are present? 5 and 5 7 and 4 7 and 5 8 and 4

38. Wrong Answer! Each oxygen atom has 2 lone pairs, so there are 8 bonds. 4 x C-H, 2 C-O, 1 X C=O

39. Congratulations!