##### Final Exam Spring 2005

Possibly useful information:

 Zero Order: [A] = –kt + [A]o First Order: Second Order: Arrhenius Equation: Kp=Kc(RT)n R = 0.0821 L•atm/mol•K R = 8.314 J/mol•K
 Eocell = Eored + Eoox Go = –nFEo nF = At F = 96485 coul/mol
3
 pH = –log[ H3O+ ] pOH = –log[ OH– ] pH + pOH = 14.00 at 25 oC Kc = Ka(acid)/Ka(conjugate acid) Acid Ka Salt Ksp Complex ion Kf HCN 6.2×10–10 Al(OH)3 1.3×10–33 [Fe(EDTA)]2– 2.1×1014 H3PO4 7.1×10–3 Zn(OH)2 1.2×10–17 [Fe(EDTA)]– 1.7×1024 H2PO4– 6.3×10–8 [Al(OH)4]– 1.1×1033 HPO42– 4.2×10–13 [Zn(OH)4]2– 4.6×1017 H2CO3 4.4×10–7 HCO3– 4.7×10–11 H2C2O4 5.4×10–2 NH4+ 5.6×10–10 Fe2+ 3.2×10–10 Fe3+ 6.3×10–3 Substance HfokJ/mol SoJ/mol•K H+(aq) 0 0 H2O(g) –242 189 H2O(l) –286 70. H3O+(aq) –286 70. H3PO4(aq) –1288 158 H2PO4–(aq) –1296 90. HPO42–(aq) –1292 –33 PO43–(aq) –1277 –222 H2CO3(aq) –699 191 HCO3–(aq) –691 95 CO32–(aq) –677 –57

1. Complete and balance the following chemical equations.

a. aqueous perchloric acid plus aqueous potassium hydroxide

b. aqueous phosphoric acid plus aqueous magnesium hydroxide

c. HCN(aq) + NH3(aq)

d. Co(CH3CO2)2(aq) + H2S(aq)

e. Fe3+(aq) + EDTA4–(aq)

f. aqueous bicarbonate ion plus aqueous cyanide ion

g. Cu(s) + HNO3(aq) Cu2+(aq) + NO2(g)

h. Al(s) + MnO4(aq) Al(OH)3(s) + MnO2(s)

g. H2C2O4(aq) + CrO42–(aq) Cr3+(aq) + CO2(g)

2. For each of the following solutions or mixtures, estimate the molar concentrations of all dissolved ions and molecular species (except water) and then estimate the pH of the solution.

a. 0.1 M hydrobromic acid

b. 0.1 M sodium hydroxide

c. 0.1 M Na2CO3

d. 0.1 M Fe(NO3)2

e. 0.1 mol Al(OH)3 placed in 1 L of water

3. A reaction, A(aq) + B(aq) products, has a rate law that is first order in each reactant at 25 oC.

a. Write the rate law for the reaction.

b. If the concentration of A is doubled, how does the reaction rate change and how does the rate constant change?

c. If the concentration of A is doubled and simultaneously the concentration of B is halved, how does the reaction rate change and how does the rate constant change?

d. If the temperature is doubled, how does the reaction rate change and how does the rate constant change?

4. Consider the reaction between hydrogen phosphate ion and carbonate ion.

a. Write the balanced reaction.

b. Find Ho for the reaction.

c. Find So for the reaction.

d. Find Go for the reaction at 25 oC.

e. Show two different ways that you could calculate the equilibrium constant for the reaction using data provided on this exam. Then use one of these methods to determine the equilibrium constant.

5. Consider the reaction:

[Al(OH)4](aq) + Zn(s) [Zn(OH)4]2–(aq) + Al(s)

a. Write the balanced oxidation half-reaction in base.

b. Write the balanced reduction half-reaction in base.

c. Write the balanced net reaction in base.

d. Write the cell notation for the reaction at standard conditions.

6. Briefly answer the following questions:

a. Zn(OH)2 is more soluble in a solution that is buffered with pH = 10 than in a solution that is not buffered with pH = 10. Explain.

b. A solution of hydrochloric acid with pH = 4 and a solution of acetic acid with pH = 4 are prepared. If equal volumes of each solution are titrated with 0.1 M sodium hydroxide, which solution requires more base and why?

c. H+ and H3O+ are used interchangeably to represent the cationic autoionization product of water and any associated chemical reactivity. Despite this, the thermodynamic parameters for the two ions are different. Suggest an explanation.

d. What does entropy measure?