Chemistry CP Final Exam Review #2 Chapter 10: Energy Define the following terms: energy, potential energy, kinetic energy, radiant energy, Law of conservation of energy, state function, temperature, heat, exothermic reaction, endothermic reaction, calorie, specific heat, enthalpy, calorimeter, Hess’s Law, fossil fuels, petroleum, natural gas, coal, greenhouse effect, entropy Problems: Use the specific heat equation to compete the following problems. Q = m x C x T (Remember: C = 4.184 J/g*C for water) 1. The temperature of a metal bar with a mass of 87 grams is raised from 31oC to 132oC. In the process, 790.0 Joules of heat were absorbed. Find the specific heat of the metal. 790.0 J 87 g C 132 o C 31o C C = 0.090 J/g*C 2. How much heat is required to raise the temperature of an 18.7 gram sample of platinum by 2.3oC if the specific heat of platinum is 1.3 J/g.oC? J q 18.7 g 1.3 o 2.3o C g* C q = 56 J 3. A 23.6 g sample of metal, originally at 88.0oC, was places in 62 grams of water originally at 17.0oC. After some time, the system reached equilibrium and the final temperature of the system was 21.5oC. Find the specific heat of the metal. qmetal = qwater 23.6 g C 88.0 o C 21.5o C 62 g 4.184 C = 0.74 J/g*C J 21.5 o C 17.0C o g C Use Hess’s Law to complete the following problems. 4. Calculate the Enthalpy change for the reaction, N2 (g) + 2 O2 (g) 2 NO2 (g) , given the information below. N2 (g) + O2 (g) 2 NO(g) H = 180 kJ 2NO(g) + O2 (g) 2 NO2 (g) Add reactions N2 + 2 O2 2 NO2 H = -112 KJ H = 68 kJ 5. Find the H for the reaction: 2 Cu(s) + O2 (g) 2 CuO(s) reverse reaction reverse and X 2 4 CuO(s) 2 Cu2O(s) + O2 (g) Cu2O(s) Cu(s) + CuO(s) 2 Cu2O + O2 4 CuO H = 288 kJ H = 11 kJ H = -288 kJ 2 CuO + 2 Cu 2 Cu2O H = -22 kJ __________________________________________ 2 Cu + O2 2 CuO H = -310 kJ Complete the following heat and stoichiometry problems: 6. Nitrogen reacts with hydrogen to produce ammonia (NH3). Ho = -46.2 kJ. How many kJ of heat is absorbed when 97 grams of NH3 is produced? (Hint: write the reaction first.) N2 + 3 H2 2 NH3 1 mol NH 3 46.2 kJ 130 kJ 17.0305 g NH 3 2 mol NH 3 97 g 7. How much heat is transferred when 9.22 grams of glucose (C6H12O6) in your body reacts with O2 to produce CO2 and H2O? (Ho = -2500 kJ) (Hint: write the reaction first.) C6H12O6 + 6 O2 6 CO2 + 6 H2O 1 mol C6 H 12O6 2500 kJ 130 kJ 180 . 158 g C H O 1 mol C H O 6 12 6 6 12 6 9.22 g C6 H12O6 Chapter 11: Modern Atomic Theory Define the following terms: electromagnetic radiation, wavelength, frequency, photons, quantized, line spectrum, continuous spectrum, orbital, principal energy levels, sublevels, electron configuration, orbital diagram, valence electrons, core electrons, representative elements, metals, nonmetals, metalloids, atomic size, ionization energy 1. Describe the Rutherford model of the atom The Rutherford model of the atom consists of a centrally located nucleus, which contains most of the atom’s mass including the positively charged protons and neutral neutrons. Negatively charged electrons orbit the nucleus in circular paths. The number of protons and electrons is equal and the atom is mostly empty space. 2. Describe the Bohr model of the atom. The Bohr model of the atom describes a positively charged nucleus with negatively charged electrons traveling in circular orbitals, which correspond to distinct energy levels. When excited, electrons can move to higher energy level orbits. 3. Describe the Wave-mechanical model of the atom The Wave-mechanical model of the atom treats the electrons as particles, which move in the form of a wave. The electrons are located outside of the nucleus and travel randomly throughout atomic orbitals. These orbitals describe regions of space in which the probability of finding an electron is likely. 4. Draw orbital diagrams for the following elements and determine the number of unpaired electrons. a. Magnesium Draw with boxes for oribtals and arrows representing electrons! 12 electrons, 0 unpaired b. Oxygen 8 electrons, 2 unpaired c. Aluminum d. Argon 13 electrons, 1 unpaired 18 electrons, 0 unpaired e. Scandium 21 electrons, 1 unpaired 5. Write electron configurations for: a. Lead 1s22s22p63s23p64s23d104p65s24d105p66s24f145d106p2 b. Nickel 1s22s22p63s23p64s23d8 6. Describe the trends on the periodic table for atomic size and explain why elements follow these trends. Atomic Size increases going down a group on the periodic table and decreases going left to right across the periodic table. As you go down a group the outer electrons are in successively higher energy levels and, therefore, larger orbitals. As you go left to right across a period, elements contain outer electrons in the same energy level. However, the number of protons increases, resulting in a greater attraction for the outer electrons and making the atoms smaller. 7. Describe the trends on the periodic table for ionization energy and explain why elements follow these trends. Ionization energy increases as you go up a group on the period table and left to right across the periodic table. Moving up a group, the I.E. increases because outer electrons are in smaller orbitals and, therefore, closer to the nucleus and held more strongly. As you go left to right, the I.E. increases because the number of protons in the nucleus is increasing. This results in a greater positive charge that attracts outer electrons. It can also be explained in terms of size. The smaller the atom is, the larger the ionization energy. As atoms get smaller the outer electrons can be closer to the nucleus and attracted strongly to the nucleus.