Term test #2 (50 points) Friday, June 24, This test has 10 questions and you have 50 minutes.

Transcription

1 Term test #2 (50 points) Friday, June 24, 2011 This test has 10 questions and you have 50 minutes. A calculator and periodic table may be used as required. Please use figures whenever possible illustrate your answers. Name: Student ID

2 Chem 222 Intro to Inorganic Chemistry 2 Page or Question Total Mark Grade Total 50

3 Chem 222 Intro to Inorganic Chemistry 3 1 (8 points) a) The gain of electrons is known as an and in an electrochemical cell occurs at the. b) If the cation radius remain constant, but the, the favoured crystal structure changes and the coordination number of the cation increases. c) The reactivity of an element generally as one moves down a group. d) For any solid state structure comprised of a single type of sphere there are a total of seven possible and fourteen. e) A superoxide has a chemical formula of. f) Metallic radius in different crystal structures differ as the coordination number changes. The lattice structures (BCC, SC, FCC) in order of decreasing metallic radii are. d) ZnSe would be most likely to prefer a crystal structure. e) When considering the strength of ionic interactions in crystals, the constant is a constant that varies with crystal type.

4 Chem 222 Intro to Inorganic Chemistry 4 2. a) (4 points) For these pairs of elements or compounds, circle the one likely to have a higher melting point. Briefly justify your answers and name the specific bonding force responsible for each. (a) NaCl CaO (b) CHCl 3 CHF 3 b) (2 points) You are carrying out a reaction and using solid Na as a reagent to produce a desired product. However, the melting point is too high and the reaction proceeds too slowly. Suggest another element to use, justify your choice based on fundamental principles and describe the bonding responsible.

5 Chem 222 Intro to Inorganic Chemistry 5 3. (4 points) Potassium bromide crystallizes in the NaCl structure depicted below. Calculate the number of K+ and Br- ions in the unit cell and determine if this matches the stoichiometry. What is the coordination number of the anion and the cation in this species?

6 Chem 222 Intro to Inorganic Chemistry 6 4. (12 points) Do THREE of the following FOUR questions and clearly indicate which one you are not doing. Use figures where appropriate. (a) The radius of an element has an effect on the melting point of the resulting solid state structure. However an increase in radius within a given group can result in either an increase or a decrease in melting point. Give specific examples of each and explain why two opposite trends are observed. Be clear as to the type of bonding and how the bonding works. (b) Give the anodic reaction, the cathodic reaction and the balanced overall reaction for the electrochemical synthesis of magnesium(ii)chloride from magnesium and chlorine gas.

7 Chem 222 Intro to Inorganic Chemistry 7 (c) TiCl4 is a gas, while ScCl3, CaCl2 and KCl are solids. Why? Discuss the expected structure and properties of VCl 4. (d) Estimate the ionic radius of Cl -. The lattice energy of CsCl is 633 kj/mol. For CsCl the Madelung constant is and the Born exponent is The ionic radius of Cs + is 1.69 Angstroms.

8 Chem 222 Intro to Inorganic Chemistry 8 5. (a) (4 points) Sketch a FCC lattice structure in the cube below. Draw and label a line that depicts r and one that depicts 4r. (b) (4 points) Calculate the % occupancy of a BCC (shown below). Show all calculations. BCC d 2 atoms/cell d=4r Fe = 3a BCC radius of each sphere = r diagonal length of unit cell = r+2r+r = 4r=d d= 3a= 4r edge length (a) = 4r/ 3 = 4r/1.73 = 2.31r volume of cell = a 3 = 12.33r 3 % occupancy = 2 sphere/unit cell = 2(4.19r 3 /12.33r 3 ) x 100% = 68%

9 Chem 222 Intro to Inorganic Chemistry 9 6. (6 points) Fill in the reactants or products of these reactions, including their phase (s, l, aq, g), to give balanced overall reactions. (Note: you may also need to adjust the reactants or products stoichiometries to balance the equations.) Assume sufficient heat is available to initiate the reactions. If no reaction occurs, please note that. (a) K (s) + O 2 (g) (b) Mg (s) + O 2 (g) (c) CaO(s) + CO 2 (g) (d) K (s) + Cl 2 (g) (e) I 2 (s) + KI(aq) (f) XePtF 6

10 Chem 222 Intro to Inorganic Chemistry (6 points) List A below contains words or phrases, some of which have a partner in list B. Match the items in List A with their partners in List B. List A: HF, HCl, Na, Br 2, F, CaO, Ne, He, I 2, Al, Fe, Ca, Cs List B Fuming brown liquid Reacts with hot water to generate an alkaline solution and hydrogen gas. Will react very slowly with room temperature water. Least reactive element in the periodic table Glows with a bright white light when heated Metallic element that is a liquid at body temperature Weak acid that is extremely toxic.