NJC 2023 H1 Chemical Bonding Tutorial Answer

National Junior College SH1 H1 Chemistry 1 CHEMICAL BONDING TUTORIAL Interatomic Bonding 1 Using the list below, give one example to each of the following solid lattices showing the given properties. Name the structure and type of bonding found in each lattice. graphite, diamond, copper, iodine, sodium chloride (a) A hard and brittle solid. (b) A solid that conducts electricity and melts at 1085oC. (c) A solid that cuts through metal and does not conduct electricity. (d) A substance that sublimates when heated. (e) A solid that can be used as a lubricant. Structure Bonding type Example (a) ionic lattice Ionic bonding NaCl (b) metallic lattice Metallic bonding Cu (c) Giant molecular structure Covalent bonding Diamond (d) Simple molecular structure • Covalent bonding within molecule • Weak intermolecular force of attraction between molecules I2 (e) Giant molecular structure • Covalent bonding between atoms within a layer • Weak intermolecular force of attraction between layers Graphite 2 Which statement(s) are correct? I HCl (g) can conduct electricity. II Covalent bond is a weak bond compared to ionic bond as boiling point of H2O is lower than that of MgO. III Ionic bonds and covalent bonds can both occur in the same compound. IV Metals can be distinguished from ionic compounds by their electrical conductivity in the solid and liquid state. A Statements I and III are correct. B Statements II and IV are correct. C Statement III and IV are correct. D Statements I, III and IV are correct I False. HCl (g) has simple molecular structure with no mobile charge carrier. HCl can dissociate into ions H+(aq) and Cl−(aq) in water, and conduct electricity in aq state. II False. Both are strong bonds. The boiling of H 2O involves only the breaking of the weak hydrogen bonds between the H 2O molecules. However, the strong ionic bo nd is overcome in MgO when it undergoes phase change during boiling point.

National Junior College SH1 H1 Chemistry 2 III True. Eg. Na2SO4. Ionic bonds between Na+ and SO42– ions, covalent bonds between S and O in SO42– ion. IV True. Metals conduct electricity in molten and solid state, while ionic compounds conduct electricity in molten state, not in solid state. Hence, this can be used to distinguish metal from ionic compounds. 3 Boron trifluoride and ammonia reacts in a 1:1 mole ratio to form a single compound. Describe the type of bond formed during this reaction. N atom in ammonia forms a dative bond to B atom in BF3. B atom in BF3 is electron deficient, hence B attains the octet by accepting a lone pair from N in ammonia into its empty p-orbital. 4 Explain the following observations in terms of structure and bonding. i. MgO has a higher melting point than NaCl. Both MgO and NaCl have ionic lattice structures. • Product of charges (q+ × q−) is larger for MgO and interionic distance (r+ + r−) i