Saturday, May 7, 2011

Chem II: Final Exam Review (Part 3/4)




(quick links to all 4 parts)


Ch. 12 and 13 Practice Test (Solutions and Rates of Reaction) 

Chapter 14-16 Practice Test (Part 2: Chemical Equilibrium, Acids and Bases, and Acid-Base Equilibria)

Chapter 17 and 18 Practice Test (Part 3: Solubility and Complex-Ion Equilibria, and Thermodynamics and Equilibrium)

Chapters 19, 20, and 23 Practice Test (Part 4: Electrochemistry, Nuclear Chemistry, and Organic Chemistry)




Chapter 17 and 18 Practice Test
(Part 3: Solubility and Complex-Ion Equilibria,
and Thermodynamics and Equilibrium) 

1.       Write the Ksp expression and x-formula for the following salts:
a.       Ca(OH)2
                                                               i.      Ksp = [Ca2+][OH-]2
                                                             ii.      Ksp = (x) * [(2x)2]
b.      Na3PO4
                                                               i.      Ksp = [Na+]3[PO43-]
                                                             ii.      Ksp = [(3x)3][x]
2.       What are Ksp and Qsp, and what is the difference between them?
a.       Ksp = Product Solubility Constant, it tells you the solubility of a salt in water at equilibrium. It may be used to tell if a precipitate will form upon at equilibrium.
b.      Qsp = Reaction Quotient, Ratio of Products over reactants at instant of mixing. Can also be expressed as Qip to determine if a precipitate will form upon the instant of mixing.
c.       If Qip > Ksp, then the solution is super-saturated (precipitate forms)
d.      If Qip = Ksp, then the solution is saturated and at equilibrium.
e.      If Qip < Ksp, then it is unsaturated, and there is no precipitate.
3.       45mL of 0.015M CaCl2 is added to 55mL of 0.010 M Na2SO4.
a.       What is the Qip?
                                                               i.      3.71 x 10-5
b.      What is the Ksp?
                                                               i.      2.4 x 10-5
c.       Will a precipitate form, and why or why not?
                                                               i.      Qip > Ksp, so a Precipitate will form.
4.       The solubility of magnesium oxalate, MgC2O4 in water is 0.0093 mol/L. Calculate Ksp
a.       8.65 x 10-5
5.       The solubility of silver chromate, Ag2CrO4 in water is 0.022 multiplied by100 g/L. Calculate Ksp.
a.       1.16 x 10-12
6.       What is a complex ion, how are the formation and dissociation constants for it expressed? Give an acidic and basic example.
a.       A complex ion is an anion that is composed of a metal and one or more ligands.
b.      A ligand is a molecule or anion bound to a metal through coordination of lone pairs.
c.       The Formation Constant is Kf and the Dissociation constant Kd = 1/Kf.
d.      Typically the Kf for a complex ion is very large and the reaction goes to completion.
e.      Co(H2O)62+ - CoCl42- are both examples of a complex ion (Co) bound to ligands.
f.        The complex ion acts as a Lewis Acid, accepting elections.
g.       The ligands act as a Lewis Base, donating elections.
h.      Solubility is increased because the formation of it removes a product.
7.       The solubility of magnesium fluoride, MgF2, in water is 0.016 g/L. What is the solubility (in grams per liter) of magnesium fluoride in 0.014 M sodium fluoride, NaF?
a.       2.2 x 10-5 g/L
8.       What is the solubility of MgF2 in water? The Ksp for MgF2 is 7.4 x 10-11
a.       2.6 x 10-4 M
9.       What are the Thermodynamic State Functions?
a.       E, G, S, P, T, H, V, Qp “Every Good Student Picks The Hot Valentine Qp.”
10.   Which Thermodynamic variables are not State Functions?
a.       q (heat) and w (work).

11.   Why study Thermodynamics?
a.       It can tell us if a reaction is possible, the entropy, energy, and whether or not it is spontaneous or not. This saves us time, energy, money, and frustration.
12.   Why study Kinetics?
a.       It can tell us how fast a reaction happens, how we got there, the reaction mechanism, and collision theory.
13.   What is ∆H, and what can it tell us, and how?
a.       Enthalpy, also known as qp, and is a state function.
b.      If ∆H is negative, heat is a product and the reaction is exothermic.
c.       If ∆H is positive, heat is a reactant, and the reaction is endothermic.
14.   Are the following situations more likely to be Spontaneous or NonSpontaneous?
a.       Flow of heat from a hot place to a cold place?                     (Spontaneous)
b.      State change from liquid to solid?                                             (Non-Spontaneous)
15.   What is Gibb’s Free Energy Equation and what must be remembered?
a.       ∆G = ∆H - T∆S
b.      Remember ∆S is in Joules, not KiloJoules.
c.       ∆G = 0 at equilibrium.
16.   How can Gibb’s Equation be used to determine K , and what must be remembered?
a.       ∆G = -RT ln(K)
b.      Ln(K) = ∆G / -RT
c.       Convert ∆G to Joules, as R is our constant.
d.      ∆G = 0 at equilibrium.
17.   What are the units of measurement in the following?
a.       ∆G = kJ/mol
b.      ∆S = J/K
c.       ∆H = kJ/mol
d.      R = J/K*mol
18.   What is the 1st Law of Thermodynamics and its associated formula?
a.       Energy can neither be created nor destroyed.
b.      Change in Internal Energy (∆u) is equal to the heat of the reaction plus the work done to the system.
c.       ∆u = q+w        (Internal Energy = Thermal + Kinetic Energy.)
19.   What is the 2nd Law of Thermodynamics and its associated formula?
a.       Entropy will increase if a process is spontaneous.
b.      ∆S > (q/T) is a spontaneous reaction
c.       ∆S = (q/T) is an equilibrium reaction
d.      ∆S < (q/T) is a non-spontaneous reaction
20.   What is the 3rd Law of Thermodynamics and its associated formula?
a.       Entropy will increase with temperature.
b.      The Entropy of a perfectly ordered crystalline substance at 0 K is 0.
21.   Which anions are soluble in acidic solutions? Why? Give examples.
a.       Very Basic Anions will be more soluble in acid than water.
b.      F-, CO32-, S2-, OH-, PO+43-
c.       Weak Basic Anions will not be affected much by pH.


2.       Under what conditions do the following indicate a spontaneous reaction?
a.       K ?          (If value is greater than 1.0 x 103 it is spontaneous and favors products)
b.      ∆G          (if value is negative)
c.       ∆S           (if value is positive)

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