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1 Name: Total Points /15 1. Testing of an unknown solid shows that it has the properties listed below. (1) low melting point (2) nearly insoluble in water (3) nonconductor of electricity (4) relatively soft solid Figure 1 Explain why the particles of this substance are nonconductors of electricity. 2. Each molecule listed below is formed by sharing electrons between atoms when the atoms within the molecule are bonded together. Molecule A: Cl 2 Molecule B: CCl 4 Molecule C: NH 3 Explain why CCl 4 is classified as a nonpolar molecule. Figure 2 3. [Refer to figure 2 in question 2] Explain how the bonding in KCl is different from the bonding in molecules A, B, and C. 4. Base your answer on the electronegativity values and atomic numbers of fluorine, chlorine, bromine, and iodine that are listed on Reference Table S. Explain, in terms of electronegativity, why the H-F bond is expected to be more polar than the H-I bond. castlelearning.com/ /AssignmentPrintin 1/6

2 5. Base your answer to the question on your knowledge of chemical bonding and on the Lewis electron-dot diagrams of H 2 S, CO 2, and F 2 below. Figure 3 Explain, in terms of structure and/or distribution of charge, why CO 2 is a nonpolar molecule. 6. Base your answer to the question on the balanced equation below. 2Na(s) + Cl 2 (g) 2NaCl(s) Explain, in terms of electrons, why the bonding in NaCl is ionic. 7. Base your answer to the question on the table below. Figure 4 Explain, in terms of electronegativity difference, why the bond in H-Cl is more polar than the bond in H-I. castlelearning.com/ /AssignmentPrintin 2/6

3 8. Aluminum is one of the most abundant metals in Earth s crust. The aluminum compound found in bauxite ore is Al 2 O 3. Over one hundred years ago, it was difficult and expensive to isolate aluminum from bauxite ore. In 1886, a brother and sister team, Charles and Julia Hall, found that molten (melted) cryolite, Na 3 AlF 6, would dissolve bauxite ore. Electrolysis of the resulting mixture caused the aluminum ions in the Al 2 O 3 to be reduced to molten aluminum metal. This less expensive process is known as the Hall process. Figure 5 Explain, in terms of ions, why molten cryolite conducts electricity. 9. The particle diagrams below represent the reaction between two nonmetals, A 2 and Q 2 Figure 6 Identify the type of chemical bond between an atom of element A and an atom of element Q. castlelearning.com/ /AssignmentPrintin 3/6

4 10. Figure 7 Explain why Lewis electron-dot diagrams are generally more suitable than electron-shell diagrams for illustrating chemical bonding. castlelearning.com/ /AssignmentPrintin 4/6

5 11. Carbon and oxygen are examples of elements that exist in more than one form in the same phase. Graphite and diamond are two crystalline arrangements for carbon. The crystal structure of graphite is organized in layers. The bonds between carbon atoms within each layer of graphite are strong. The bonds between carbon atoms that connect different layers of graphite are weak because the shared electrons in these bonds are loosely held by the carbon atoms. The crystal structure of diamond is a strong network of atoms in which all the shared electrons are strongly held by the carbon atoms. Graphite is an electrical conductor, but diamond is not. At 25 C, graphite has a density of 2.2 g/cm 3 and diamond has a density of 3.51 g/cm 3. The element oxygen can exist as diatomic molecules, O 2, and as ozone, O 3. At standard pressure the boiling point of ozone is 161 K. Figure 8 Explain, in terms of electrons, why graphite is an electrical conductor and diamond is not. Your response must include information about both graphite and diamond. 12. Bond energy is the amount of energy required to break a chemical bond. The table below gives a formula and the carbon-nitrogen bond energy for selected nitrogen compounds. Figure 9 State the relationship between the number of electrons in a carbon-nitrogen bond and carbon-nitrogen bond energy. castlelearning.com/ /AssignmentPrintin 5/6

6 13. Carbon has three naturally occurring isotopes, C-12, C-13, and C-14. Diamond and graphite are familiar forms of solid carbon. Diamond is one of the hardest substances known, while graphite is a very soft substance. Diamond has a rigid network of bonded atoms. Graphite has atoms bonded in thin layers that are held together by weak forces. Recent experiments have produced new forms of solid carbon called fullerenes. One fullerene, C60, is a spherical, cagelike molecule of carbon. Figure 10 State, in terms of the arrangement of atoms, the difference in hardness between diamond and graphite. 14. Figure 11 Explain, in terms of molecular polarity, why hydrogen chloride is more soluble than methane in water at 20. C and standard pressure. 15. [Refer to figure 11 in question 14] Explain, in terms of intermolecular forces, why ammonia has a higher boiling point than the other compounds in the table. castlelearning.com/ /AssignmentPrintin 6/6