Re: Re; dead battery

Allan Adler <ara@xxxxxxxxxxxxxxxxxxxx> wrote in
news:y9363xq8i0s.fsf@xxxxxxxxxxxxxxxxxxxx:

Allan Adler <ara@xxxxxxxxxxxxxxxxxxxx> writes:

Allan Adler <ara@xxxxxxxxxxxxxxxxxxxx> writes:
I was just reading the discussiong of manganese in the CRC
book. Apparently it was first extracted from manganese dioxide
by reducing with carbon. If the MnO2 in the battery comes with
powered carbon, as some have told me it does to improve
conductivity, then after the KOH and Zn are removed, maybe
one is nearly set up to produce elemental manganese.

It says that manganese was first separated by Gahn in 1774. Where
can I find a copy of whatever Gahn might have written about this?

According to the CRC book, the enthalpy of formation of CO2 is
-94.051 kcal/mol while that of MnO2 is -124.29, so the reaction
MnO2 + C -> Mn + C02 -124.29 kcal/mol + 94.051 kcal/mol looks like
it would not go forward. I don't do stuff like this very often, so
maybe I'm just making a stupid mistake. If not, why was Gahn able
to isolate Mn in this way?

1. Delta H's are in general T dependent, and CRC only tells you the
298K value.

2. This reaction has a large positive delta S, due to formation of
gaseous product. You need to consider the delta G for the reaction,
not just the delta H.

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Relevant Pages

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