CHEM 281(01) SPRING 2003. HOMEWORK 7. CHAPTER 8.
  1. Figure out the driving force for following reactions.
    2. a) 3NaOH + H3PO4 ---> Na3PO4 + 3H2O
    b) Na2CO3 + 2HCl ---> H2O + CO2(g) + 2NaCl
    c) NH4Cl + NaOH ---> NH3(g) + H2O + NaCl
    d) Na2SO4 + Pb(NO3)2 ---> PbSO4(s) + 2NaNO3
    e) Zn + 2HCl ---> ZnCl2 + H2
  2. Identify the conjugate acid/base pairs in following reactions.
    3. a) HF(aq) + H2O ---> H3O+(aq) + F-(aq)
    b) H2O(l) + NH3(aq) ---> OH-(aq) + NH4+(aq)
    c) H2Fe(CO)4 + CH3OH ---> [FeH(CO)4]- + CH3OH2+
    d) NH3 + H2S ---> NH4+ + HS-
  3. Calculate DG0 for autoprotolysis of H2O and NH3 using values of Kw = 1x10-14 and

    4. Kam = 1x10-33. Which compound is the stronger acid?
     
  4. A acid HB is dissociating according to the following equation in water.

    5.  

     

    HB(aq) <--- H+(aq) + B-(aq)

    A solution of HB was prepared by dissolving 1.00 mol of HB in 1 liter of water. After the equilibrium is established HB was found to be 20% dissociated. Calculate Ka and pKa for the acid HB.
     

  5. Arrange the following compounds in order of increasing acidity:

    6.  

     

    HI (pKa = -11), H2CO3 (pKa = 6.37), H2SO3 (pKa = 1.81), HCN (pKa = 9.31)
     

  6. Explain the trend shown by following binary acids in water:

    7.  

     

           HF      HCl       HBr     HI

    pKa     +3      -7       -9      -11

            NH3     H2O       HF

    pKa     +33     +14       +3
     

  7. Which acids of the following pairs of acids is the stronger acid?

    8.  

     

    a) [Fe(OH2)6]3+/[Fe(OH2)6]2+ b) Al(OH2)63+/Ga(OH2)63+ c) Si(OH)4/Ge(OH)4 d) HClO3/HClO4
    e) H2CrO4/HMnO4 f) H3PO4/H2SO4 g) H2SO4/H2SeO4 h) HIO4/HClO4
     

  8. Which of the following elements form oxide polyanions and which forms oxide polycations? Al, As, Cu, Mo, Si, B, Ti
  9. Identify the Lewis acids and bases in following reactions:
    10. a) BrF3 + F- ---> BF4-
    b) BF3 + NH3 ---> F3B-NH3

    c) FeCl3 + Cl- ---> FeCl4-
    d) I- + I2 ---> I3-
    e) (SnCl3)- + (CO)5MnCl ---> (CO)5Mn-SnCl3 + Cl-
  10. Explain why Na+ prefers F- to I- where as Cu+ prefers I- to F-.
  11. Consider the Lewis acids (CH3)3Al and (CH3)3Ga and the Lewis bases (CH3)3N, (CH3)3P, and (CH3)3As.


    12. (CH3)3Al will react most favorably with ______________.

    (CH3)3Ga will react most favorably with ______________.

  12. Explain the reaction sequence given below in terms of hard and soft Lewis acid-base behavior:


    13. AgCl         AgF
               R3SiNC ---- R3SiCl ---- R3SiF

  13. Explain why HF acid is used to make marks and dissolve glass.


    14. Which of the following metal expected to be found in alumino silicate minerals and which in sulfides? Cd, Rb, Cr, Pb, Sr, Pd

  14. Propose routes for following preparations.


    15. a) C2H2 from CaC2 b) P(CH3)3 from PCl3

  15. Explain the Lewis acidity observed in the following series:


    16. BF3 < BCl3 < BBr3

    SiI4 < SiBr4 < SiCl4 < SiF4

  16. Explain the role of Al2Cl6 as a Lewis acid in Friedel Craft Acylation of benzene.