Chapter 11Short Answer:1. What characteristic distinguishes an element from a compound?2. What type of process is involved in going from element to compounds and viceversa?3. When sugar is dissolved in iced tea what is the solvent and what is the solute? Whenwould you become aware that the solution is saturated?4. About how many elements are known at present? About how many occur naturally inour environment?5. Name the scientist who receives the major credit for the development of the periodictable. In what year as his work published?6. At first the periodic table placed the elements in order of increasing atomic mass.What property is now used instead of atomic mass?7. Why are chemists so interested in the number of valence electrons in atoms?8. Briefly why do elements in a given group have similar chemical properties??Exercises:1. Classify each of the following materials as an elements compound heterogeneousmixture or homogeneous mixture: (a) air (b) water (cd) diamond (d) soil2. Give the name of each element: (a) N (b) K (c) Zn3. Refer to the periodic table and give the period and group number of each of theseelements: (a) neon (b) barium (c) iodine4. Give the total number of electrons the number of valence electrons and the numberof shells containing electrons in (a) a silicon atom and (b) an argon atom. Chapter 12Short Answer:1. State the law of conservation of mass and give an example.2. The atomic masses of the elements in the periodic table are measured relative to anatomic mass standard. Name the isotope that is used as the atomic mass standard andgive its assigned mass in atomic mass units (u).3. State the octet rule. What common element is an exception to this rule and why?4. How is the number of valence electrons in an atom related to its tendency to gain orlose electrons during compound formation?5. Briefly how are covalent compounds formed?6. A covalent bond is which the electron pair is unequally shared is called by whatname?7. The density of a solid substance is usually greater than its density in a liquid form yetthe density of liquid water is greater than the density of solid water (ice). Explain.Exercises:1. Volcanoes emit much hydrogen sulfide gas H2S which reacts with the oxygen in theair to form water and sulfur dioxide SO2. Every 68 tons of H2S reacts with 96 tons ofoxygen and forms 36 tons of water. How many tons of SO2 are formed?2. Find the percentage by mass of C1 in MgC12 if it is 25.5% Mg by mass.
