You will be given 90 minutes to complete the examination. In problems requiring a derivation or a calculation, you will be expected to show your work to obtain credit. Pay particular attention to significant digits and units. A periodic table of the elements and the values of fundamental constants will be provided. The use of a calculator is permitted on this examination. N.B. Students taking the Advisory Examination for Chem 1a are NOT permitted to use a calculator.

1. Balance the following oxidation-reduction equation. The reaction is carried out in a strongly acidic aqueous medium. Draw a rectangle around the oxidizing agent and a circle around the reducing agent.
   Cr₂O₇^-2(aq) + I^-(aq) = Cr⁺³(aq) + I₃^-(aq)

2. Aluminum metal dissolves in aqueous hydrochloric acid to yield gaseous hydrogen and aluminum(III) ions according to the following unbalanced ionic equation:
   Al(s) + H⁺(aq) = H₂(g) + Al⁺³(aq)
   • Calculate the minimum volume of 0.2000 M HCl required to dissolve 3.00 g of aluminum.
   • Calculate the volume of gaseous hydrogen produced at 25.5 ºC and 0.985 atm when the 3.00 g of aluminum is dissolved.

3. Short answers
   • Arrange the following elements in order of increasing atomic radius (smallest radius to the left): Rn Ge Li Se He Mg
   • Give the formulae of the following compounds:
     
     • perbromic acid
     • barium sulfate
     • acetic acid
     • zinc phosphide
   • Give the electronic (orbital) configuration of ground electronic state vanadium.
   • What are the dominant species in an aqueous solution of each of the following compounds: HF, H₃PO₄, Na₂O, NH₂NH₂,

4. A reactor is filled with 2.0 atm of gaseous hydrogen and 0.015 atm of gaseous chlorine. At the temperature of the reactor, the equilibrium constant for the reaction
   H₂(g) + Cl₂(g) = 2 HCl(g)

   is 5.0 x 10^5. Calculate the partial pressure of Cl₂, H₂, and HCl when the system reaches equilibrium.

5. An unknown organic compound has the composition 70.6 wgt-% C, 13.7 wgt-% H, and 15.7 wgt-% O. When 0.0500 g of the compound is dissolved in 2.5000 g of benzene, the solution freezes at 4.05 ºC. Pure benzene freezes at 5.12 ºC. k_f, the freezing-point depression constant, of benzene is 5.48 ºC/molal.
   • Determine the empirical formula of the compound
   • Determine the molecular weight of the compound.
   • Determine the molecular formula of the compound.

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