From: Rabid Wombat <wombat@mcfeely.bsfs.org>
Date: Wed, 28 Jan 1998 15:18:52 +0800
To: "Paul H. Merrill" <paulmerrill@acm.org>
Subject: Re: State of the Union Address
In-Reply-To: <34CE676C.2B10424F@acm.org>
Message-ID: <Pine.BSF.3.91.980127113443.14544C-100000@mcfeely.bsfs.org>
MIME-Version: 1.0
Content-Type: text/plain





On Tue, 27 Jan 1998, Paul H. Merrill wrote:

> Rabid Wombat wrote:
> > 
> > On Sat, 24 Jan 1998, Matthew Ghio wrote:
> > 
> > > Anonymous wrote:
> > >
> > > > [1] Grab a totally random sample of 100 high school students. Haul the
> > > >     students out one at a time and ask them the following questions:
> > > [snip]
> > > > 11) Michelle mixes one gram of HCl and one half gram of NaOH. Under normal
> > > >     circumstances, what is produced and in what quantities?
> > > >
> > >
> > > The correct answer is an explosion and a big mess.  One student in my high
> > > school chemistry class learned this the hard way.  :)
> > >
> > >
> > 
> > Um, salt water explodes?
> 
> I guess those high school students aren't the only ones with no clear
> idea of the way the world works.  While salt water does not ordinarily
> explode, in this case salt water is the ultimate product -- but massive
> heat released when acids and bases join and recombine to produce salts
> (in this case table salt) and water.
> 
> while some do feel (especially on this list) that the ends justify the
> means -- this is one means that definitely does not go along with that
> "rule".
> 
> PHM.
> 

Actually the qustion is probably hosed, as the ratio should be 1:1
Hcl:NaOH mol, not weight (which would be about 10:9 Hcl:NaOH or so if I'm
not confused here) ...  the idea being that if you calculate and measure
just right, you can mix too highly dangerous chemicals and will get
saltwater which you can drink. If you don't measure just right, and drink
it, you are rightly fucked, so don't try this at home. 

Can't find exact delta-h listed for NaOH, but rough guess on this reaction
is maybe 150,000 - 175,000 joules, or about half a box of kitchen matches
worth of heat (~150-175 btu ?), which wouldn't boil a quart of water. I
suppose if you had a small enough solution you could get a small "bang"
out of vaporizing the water. Not exactly a terrorist threat.

A moderate amount of heat, but without increasing the number of 
molecules, where's the explosion? Am I missing something? Looks like warm 
saltwater to me. OTOH, I don't know anything about chemistry 'cuz I 
always got kicked outa class for doing dumber things than mixing Hcl and 
NaOH and drinking it, which is the usual stunt. Don't try this at home, 
and don't take chemistry advice from marsupials.

btw - didn't really "do the math" on this, and it's 2am, so it could be 
wildly innacurate.

-r.w.