Re: Combustion Stoichiometry -- Incomplete Information



johnwbarrett0112358@xxxxxxxxx wrote:
> The point that stumps me is that the problem states the amount of
> carbon dioxide and water produced as a result of the complete
> combustion (i.e. implicates excess oxygen). They also provide the
> molecular mass of the compound limonin. Unfortunately, I can't figure
> out a way to determine the amount of oxygen which is contributed by the
> oxygen in limonin and the amount contributed by the atmospheric oxygen.

OK. I squinted at the screen for a
minute or so and here's my SWAG:

First, I believe you'd want to
consider the combustion taking
place in a thingy made by Parr
for the last generation of
chemists, where a known mass
of known material is combusted
in a closed system filled with
pure oxygen and the temperature
change of a surrounding known
volume or mass of water. The
phrase "complete combustion" is
used in that venue for determinations
of thermodynamic values IIRC.

Then, I wish I had the time to
work on this poser. I'd first
try to calculate on the basis of
all the O2 coming from outside
the molecule being fried. The
answer will be wrong, or course,
but by how much -- a small decimal
amount, a large decimal amount (it'd
have to be a fractional value, else
you couldn't tell it was the wrong
answer, right?). Then, you'd have a
wrong answer for the number of oxygen
atoms in the burned material, but the
true value for C and H (this is a
SWAG, remember). After that, adjust
the number of oxygens in your sample
iteratively until you get closure,
like whole numbers for a reasonable
number of the constitutent atoms, and
a reasonable MW and structure.

OTOH, you could be the victem of
an innocent or not-so-innocent
TYPO _and_ my hyperbole.

> The "A" in the mathematical equation should have been a lower case "a."
> This was my attempt to derive a generalized equation for calculating
> the coefficients of a standard combustion reaction of the form stated.

That may work, I don't know. Sounds
like a lot of extra effort, although
if you do your own programming, it
might do the iterations I had suggested.

Where did you find the problem(s) and
at what level of teaching? Reliable
source?

> Unfortunately, I don't think enough terms are defined.

Oops, I just excised part of your
post on this touchy laptop, but to
continue ... all the information you
need may be there, just not in the
sort of plug-n-chug format you are
expecting.

My use of the education I received
is in applying the tools I learned
in dealing with atomic/molecular
systems in unknown venues and
trying to characterize the situation
in a rational way, is in dealing with
the human animal -- devising clever
experiments (read "bashing with large
tools until it trips itself up" :-)
to elicit information that gives two or
more self-consistent results or concepts.

One experiment, one point. Two, two.
Etc.

With one point, you sit on it an
rotate (remember that old line?).
With two points you can draw
a line, pace back and forth.
Three (non colinear, i.e. distinctly
different results) and you got
a surface to walk, sit, sleep,
ponder on.

[snip]

Not sure you've got enough data?
Try a different tool/approach.


Atty
Tyson Foods Chair for Advanced Speculation
Eotvos Institute of Theoretical Charm and Beauty
At an undisclosed hard site somewhere in this galaxy.

.

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