EXAM II CHM 333 Due 10-27 by 9:00am. This is not an open book exam, and you must complete this exam on your own! You may consult your class notes at any time. 1.    The first thing you need to look at is the effect of a common ion on the solubility of a       sparingly soluble salt. First you need to do this calculation using just concentration.

a.    Consider the compound Hg₂I₂ (K_sp = 1.1 x 10^-28). Now calculate solubility in
        solutions containing 1.0M NaI to 1 x 10^-6M NaI. Show the results numerically and
        on a graph.
b.    Now we are going to consider activity. Use the Debye-Huckel equation to calculate
        the activity coefficient as a function of ionic strength µ, use values of
        µ = 0.0001, 0.0002, 0.0003, 0.001, 0.002, 0.003, 0.01, 0.02, 0.03, 0.1,0.2,0.3,0.5 Assume ionic charge ±1, then ±2, ±3, and ±4, and use a size = 500pm for all. Plot vs log µ.
c.      Now reconsider part a. calculating activity instead of concentration at the
        different ionic strengths. Again show the trend on an appropriate graph.
 
 

2.            This problem has to do with complex ion formation, and its effect on solubility.
                Consider the compound Hg₂I₂. Experimental evidence shows that at high
                concentrations of I-, more Hg₂I₂ is dissolved. There are five species believed to
                effect solubility: K_sp = 1.1 x 10^-28 K₁ = 75 B₂ = 250 B₃ = 1500 B₄ = 10000 B₅ = 50000

a.   First write the appropriate equilibria
b.   Now calculate the total amount of Mercury in a solution containing various concentrations from 10.0M I^- down to 1 x 10^-9M I^- . This must be done using a spreadsheet properly, and you need to generate a graph that best represents the data.
c.    Identify the concentration which has the following;
• The most total dissolved mercury
• The least total dissolved mercury
• The highest concentration of dissolved Hg₂²⁺

 
 

3.        This question is on the UV/VIS

a.    Draw a schematic diagram of a UV/VIS spectrophotometer with appropriate
        labels for each component.
b.    Explain Beer's Law
c.    Explain a calibration curve
d.    Why would you use the standard addition method
 
 
 
 

4.         Finally a question about charge balance and mass balance
            Consider the dissolution of the compound X₂Y₄, which might give the following species
            in aqueous solution: X₂Y₃²⁺, X₂Y₄ (aq), X₂Y₂⁴⁺, X₂Y⁶⁺, Y^2-
 

a.        Write the charge balance for the system
b.        Write the mass balance in terms of [Y^2-]. You must start by figuring
            out the relationship Y_total = __ X_total then plug in all forms of both, reduce as
            much as possible.