Sample Exam #3

1. Iodine is prepared both in the laboratory and commercially by adding Cl₂ to an aqueous solution of sodium iodide according to

            2 NaI    +    Cl₂       ®      I₂    +    2 NaCl

How many grams of sodium iodide must be prepared to produce 50.0 grams of iodine?

2. Given the equation

               H₂SO₄ (aq)  +     2 NaOH(aq)     ®       Na₂SO₄(aq)         +    2H₂O(l)

a.      Calculate how many grams of sodium sulfate will be formed by the reaction of 44.14 grams of sulfuric acid with 36.00 grams of sodium hydroxide

b.         If 50.05 grams of sodium sulfate are actually formed, what is the percent yield?

3. What elements have the following electron configurations?

            a. 1s²2s²2p³

                b. [Ar]4s²3d¹⁰4p⁵

                c. [Kr]5s²4d³

4. Write an electron configuration (1s²2s²…) for:

            a. Y (atomic number 39)

            b. Os (atomic number 76)

5. What is the total number of orbitals in the n = 2 shell?

6. In each set below, select the member with the smaller atomic radius:

            a. Co⁺² or Co⁺³

            b. As or Br

            c. Ca or Ba

            d. Br or Br^-

            e. Fe or Fe⁺³

            f. Ca or Ge

7. Write the formulas expected for an ionic compound formed from the two elements in each of the following:

               a. Aluminum and sulfur

               b. Barium and Iodine

               c. Cesium and fluorine

8. Determine the positive charge on the metal from the expected negative charge on the nonmetal for each of the following:

               a. Fe₂S₃

               b. CrCl₃

                c. Cu₂O

9.Write Lewis structures for:

               a. CHCl₃

               b. CO₃^2-

               c. ClO₃^1-

10. a. Draw a Lewis structure for HClO₃  (H is attached to one of the O’s).

                b. Use VSEPR to determine the geometry at the center Cl atom

   c.    Using electronegativity values, classify the following bonds as nonpolar (“pure”) covalent, polar covalent or ionic:

i.                     Cl – O

ii.                    O –.H

11. Given the appropriate electronegativities and geometries, which of the following molecules would be polar?

               a. OCl₂            O=3.5, Cl = 3.0             angular (bent ) geometry

               b. NH₃          N= 3.0, H = 2.1            3-sided pyramid

               c. CF₄          C= 2.5, F= 4.0        tetrahedral with C in center