exp 2 questions

[robert zellmer]

I've received a some questions about exp 2 report.

3)  Discussion Section:

      It's quite possible most of you didn't get the correct formula 
following the
      correct procedure.  Multiplying by a factor to get whole number 
subscripts
      might not give you a reasonable formula (within 0.1 of a whole 
number).
      For instance it's unlikely to have something like Pb_12 O_21 for 
an empirical
      formula for an ionic compound.  Generally speaking, the most positive
      charges (oxidation numbers) wouldn't exceed +8 and the most negative
      wouldn't exceed -3.  So what should you do?

      You should discuss whether your formula is reasonable.  How do you 
know?
      I've discussed what the normal charges for representative metals 
are based on
      what group they're in.  Group 3A (13) metals are usually +3 (Al is 
always +3)
      but can be +1.  Group 5A would be +5 or +3.  I discussed lead, Pb, 
in lecture
      and stated it is +2 or +4.  If you don't see the pattern, the 
charges for the
      representative metals in groups 3A-6A equals the group # or (group 
# - 2).

      Based on this you should be able to predict the normal charges for 
Sn.  That will
      allow you to predict the most likely compounds for Sn and O. Then 
look at your
      original ratio before you multiplied by the factor you used to get 
the whole number
      ratio.  Address why you might not have obtained the correct ratio?

      To give an example, iron can form a +2 and +3 ion.  This would 
give FeO and
      Fe2O3.  The Fe2O3 will result as the iron is oxidized over time 
and converts from
      Fe to Fe^2+ (it's usually oxidation state in solution, at least 
initially) and then to
      Fe^3+.  This is particularly true when there's a greater amount of 
oxygen available
      to react with the iron.

      If you've already turned in the report you can "fix" things if you 
like and turn it in
      again.  The TA will grade the most recent submission.

Dr. Zellmer
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osu.edu/pipermail/cbc-chem1250/attachments/20180124/1475cc8a/attachment.html>