Chem 121H Honors General Chemistry Hour Exam #1 NAME ID#

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Lionel Perry
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1 Not all pieces of information on this page are needed to complete this exam correctly Particle Mass/u Proton Neutron Electron Isotope Mass/u H H H C C K K K Ge Ge Au Constants and Conversions e = x C 1 ev = kj/mol c = 3.00 x 10 8 m/s 1 u = 1.66 x g N A = x k = 9.0 x109 Nm 2 C -2 1 J = 1 kg m 2 s E = ( m)c 2 1 g = x kj Miscellaneous Density of gold = g/cm 3 Density of germanium = g/cm 3 Nuclide symbols are written A n as Z E ± where A=mass number, Z=atomic number, E=elemental symbol, and ±n is the charge 1

2 I swear that I did not cheat during this examination: 1. Complete the table for the following isotopes. (2 points per blank) Isotope # p + #n 0 #e - 14 N La 57 chlorine From what you know about Coulomb s Law, predict which solid has the highest melting point in each section. (3 points each) a. NaF NaI NaBr b. MgBr 2 NaBr MgO 2

3 3. Balance the following nuclear reactions. Give the mass number, atomic number, and symbol for the missing element OR particle. (3 pts each) a. 218 Po + α 4 2 b. Silver Cd c. Fe+ He n The thermite reaction is a classic example of a redox reaction. It releases so much heat that it produces liquid iron (which cools to form a solid), and thus was a common way to weld steel together. Since both reactants are solids, this reaction will only occur if a very high temperature is first produced. The unbalanced chemical equation for this reaction is Fe 2 O 3 (s) + Al (s) Fe (l) + Al 2 O 3 (s) a. Write the balanced equation for the thermite reaction. (2 pts) b. Assign oxidation states to all atoms in this reaction. (6 pts) 5. Complete the following table by naming the compound, or by giving the molecular formula based upon the name. (2 pts each) Name potassium hydrogen carbonate sulfur hexafluoride Chemical formula NF 3 3

4 6. Mendeleev used relative atomic masses to construct an early periodic table in The idea that chemical properties were periodic functions of mass, while not correct, allowed him to predict chemical properties of elements that were then unknown. One such element is germanium (Ge, atomic number 32), a metal which was discovered in a. Chemists now know that chemical properties are not periodic functions of atomic masses, but rather of a different atomic property. What atomic property determines the identity of an element? (3 pts) b. Based on what you know of other elements in its group, circle what you predict is the correct molecular formula for germanium oxide. (3 pts) GeO GeO 2 GeO 3 GeO 4 Ge 2 O Ge 2 O 3 All of the following questions involve the element hydrogen in some way. 7. The ammonia use for fertilizers is made by reacting elemental nitrogen with elemental hydrogen. The balanced equation for this reaction is N 2 (g) + 3 H 2 (g) 2 NH 3 (g) What mass of ammonia, in grams, is produced when 1.34 mol of N 2 reacts with excess H 2? (4 pts) 4

5 8. There are 3 isotope of hydrogen, 1 H, 2 H, 3 H. The average mass of hydrogen is 1.01u. a. Which isotope is most abundant? (3 pts) b. Fill in the blank with either the same or a different (2 pts each). Each isotope has number(s) of electrons. Each isotope has number(s) of neutrons. Each isotope has number(s) of protons. 3 c. 1 H is a naturally occurring, radioactive isotope. Write out the balanced equation for its decay. Include mass number, atomic numbers, and symbols. (3 pts) 3 d. Calculate the nuclear binding energy for 1 H in kj/mol. This is the energy released when this isotope is formed from its constituent electron(s), neutron(s), and proton(s). (6 pts) 5

6 9. A solution of H 2 SO 4 (aq) is mixed with the following compounds. Write balanced chemical equations (net ionic equation are ok, if applicable) for any reactions that occur. If you predict that no reaction will occur, write N.R. (2 pts. Each) a. CuSO 4 (aq) b. NaHCO 3 (aq) c. KOH (aq) d. BaCl 2 (aq) 10. Elemental aluminum will react with the molecular compound water to form elemental hydrogen and the ionic compound aluminum hydroxide. a. Write the balanced equation for this reaction, including physical states. (2 pts) b. Which reactant gets oxidized? (2 pts) c. What is the % composition of aluminum hydroxide? (4 pts) 6

7 11. Draw a picture no words, just symbols that explains why H 2 O dissolves ionic compounds. (7 pts) 12. A compound is found to contain 40.9 % carbon, 4.58 % hydrogen and 54.5 % oxygen by weight. a. calculate the empirical formula of this compound (6 pts) b. the molecular weight of this compound is found to be g/mol. What is the molecular formula? (4 pts) 7

Note: there are 5 points of extra credit built in to this exam. 1. (4 points) For each of the following element categories, give three examples.

Exam 1 Chem 1A, Fall 2016 Fossum Name: Note: there are 5 points of extra credit built in to this exam. 1. (4 points) For each of the following element categories, give three examples. a. noble gases b.