4.8 extension questions_answers

4.8 Extension Questions - ANSWERS 1. What type of bonding would you expect for each of the following solids? a) K 2 S ionic b) SiH 4 molecular c) Zn metallic d) SiO 2 network covalent e) CaSO 4 ionic f) PH 3 molecular 2. Predict the type of solid that you would expect to have each of the following characteristics: a) greatest electrical conductivity metallic b) lowest melting point molecular c) highest conductivity when dissolved in water ionic d) lowest hardness molecular 3. What type of solid is a substance that… a) conducts electricity and has a high melting point? metallic b) does not conduct electricity as a solid but does when dissolved in water? ionic c) does not conduct electricity and has a high boiling point? network covalent d) does not conduct electricity and has a low boiling point? molecular 4. Compare and contrast the structures of the following solids: a) CO 2(s) and H 2 O (s) Both CO 2 and H 2 O form molecular crystal structures. CO 2 (s) is a cubic lattice made up of the linear CO 2 molecules, and H 2 O(s) is formed of stacks of hexagonal lattices that are made up of bent H 2 O molecules. b) NaCl (s) and HCl (s) NaCl forms an ionic crystal and HCl forms a molecular crystal. NaCl(s) is a cubic lattice made up of the linear bonds between Na + and Cl – ions, and HCl(s) has an orthorhombic lattice structure of linear H–Cl molecules. 5. Suggest a method/experiment to distinguish each of the following pairs of solids. For each experiment, state the expected outcome for each solid type. a) ionic crystal and molecular crystal Answers may vary. Sample answer: To distinguish between an ionic crystal and a molecular crystal, raise the solids to a moderately high temperature. The molecular crystal will melt before the ionic crystal. b) metallic crystal and network covalent crystal Answers may vary. Sample answer: To distinguish between a metallic crystal and a covalent crystal, test for conductivity. The metallic crystal will conduct electricity and the covalent crystal will not. c) molecular crystal and metallic crystal Answers may vary. Sample answer: To distinguish between a molecular crystal and a metallic crystal, test for malleability. The molecular crystal will break and the metallic crystal will bend. d) ionic crystal and network covalent crystal Answers may vary. Sample answer: To distinguish between an ionic crystal and a covalent crystal, dissolve both solids in water and test for conductivity. The ionic crystal will conduct electricity in solution and the covalent crystal will not.