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Inorganic : Couple of questions
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 Message 1 of 6 in Discussion 
From: MSN Nickname2122101234  (Original Message)Sent: 12/17/2004 11:45 PM
Yikes! Final coming up on Monday ! I've got a couple of questions from a practice test. I don't have the answers but I'm wondering if these reactions are correct:
 
1. A concentrated soulution of aqueous amonia is added to an aqueous solution of copper(ii)sulphate:
 
2NH3 (aq) + 3CuSO4(aq) --> N2(g) +3H2SO4(aq)
 
2. Nickel (ii) hydroxide is strongly heated... (hmm... does that mean combustion?)
 
Ni(OH)2 (s) + O2(g) --> NiO(g) + H2O(g)
 
 
And... I'm having trouble with these questions... if anyone can help me out with these (thanks a bunch):
 
3. Write a balanced reaction for the preparation of gaseous hydrogen chloride using the reaction of pure anhydrous sulfuric acid with another common inorganic compound.
 
4. Which element has a larger sixth ionization energy, P or S?


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 Message 2 of 6 in Discussion 
From: MSN Nickname2122101234Sent: 12/18/2004 2:00 AM
Umm... I've got another question I forgot to add:
 
Why is titanium tetrachloride a liqud at room temperature, even though the electronegativity difference between the elements is large?

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 Message 3 of 6 in Discussion 
From: MSN Nickname·Steve·Sent: 12/18/2004 2:48 AM
1.  This one is tricky, because there are two possible outcomes, depending on the concentration of the ammonia:

     a)  If the concentration of NH3 is not too high, you'll form a precipitate of Cu(OH)2(s).  Here are the reactions:
 
          Hydrolysis reactions of the weak base NH3 (an equilibrium):
          NH3(aq)  +  H2O(l)     NH4+(aq)  +  OH-(aq)

          Reaction of Cu2+ ion from CuSO4(aq) with the hydroxide ions:
          CuSO4(aq)  +  2OH-(aq)  -->  Cu(OH)2(s)  +  SO42-(aq)

          Or overall:
          CuSO4(aq)  +  2NH3(aq)  +  2H2O(l)  -->  Cu(OH)2(s)  +  (NH4)2SO4(aq)
 
 
     b)  If the concentration of NH3 is higher, the soluble, deep blue tetraamminecopper(II) complex forms:
          CuSO4(aq)  +  4NH3(aq)  -->  [Cu(NH3)4]SO4(aq)
 
 
 
2.  >> Nickel(II) hydroxide is strongly heated... <<

This will be a simple decomposition reaction (you have it right except O2 is not needed):
                            heat
          Ni(OH)2(s)   ----->  NiO(s)  +  H2O(g)
 

3.  This may be in your textbook in a chapter titled something like, "Chemistry of Nonmetallic Elements" or "Descriptive Chemistry of Nonmetallic Elements".  You usually get a comparison of the reaction of H2SO4 and NaF or CaF2 (forms HF), NaCl (forms HCl), NaBr (forms Br2), and NaI (forms I2).  These last reactions are more complicated.  With NaCl, we have
 
          H2SO4(l)  +  NaCl(s)  -->  HCl(g)  +  NaHSO4(s)
 

4.  First let's compare electron configurations before and after removing the outer six electrons:
 
     Before:   P   1s22s22p63s23p3       S   1s22s22p63s23p4
     After:    P6+  1s22s22p5          S6+  1s22s22p6 
 
Removal of six electrons from sulfur gives a noble gas configuration (neon), but removal of the sixth electron from phosphorus requires removing the electron from this same noble gas configuration, requiring much more energy to do.  (I6 for S is 8490 kJ/mol, while I6 for P is 21200 kJ/mol.)
 
 
Keep at it!

Steve

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 Message 4 of 6 in Discussion 
From: MSN Nickname·Steve·Sent: 12/18/2004 3:45 AM
Tetravalent titanium compouds like TiCl4 are generally covalent, rather than ionic.  If we look at the difference in the electronegativity of titanium and chlorine, we have 3.0 - 1.5 = 1.5.  This is less of a difference than that in sodium chloride, 3.0 - 0.9 = 2.1.  In general, if the electronegativity difference D is 2.0 or greater we have ionic bonding, D between about 0.5 and 2.0 is a polar covalent bond, and D less than 0.5 is a nonpolar covalent bond.

Next we look at the molecular geometry of TiCl4, which is tetrahedral.  Thus, the molecule is nonpolar overall, despite having those polar Ti-Cl bonds.  Strong dipole-dipole interactions between the molecules therefore are not present, just the much weaker London dispersion interactions.

For more dramatic examples, look at SF6, SeF6, and TeF6, which are gases at room temperature!  It would be interesting to know what the highest molecular weight gaseous compound known is (at room temperature and pressure).
 

Steve

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 Message 5 of 6 in Discussion 
From: MSN Nickname2122101234Sent: 12/18/2004 11:13 PM
Ah, I get it! Thanks Steve!

Reply
 Message 6 of 6 in Discussion 
From: MSN Nickname·Steve·Sent: 12/19/2004 8:41 AM
OK Navi, good luck!
 
Steve

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