[pure-silver] Re: Basic Chemistry
- From: "Nicholas O. Lindan" <nolindan@xxxxxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Thu, 12 Jun 2008 17:25:03 -0500
<eroustom@xxxxxxxxxxx>
I use a hot bath to put my bottles of working
solutions in to bring them to temp.
If my solutions are all at basement temp of
60 to 64F, what should the hot bath be at to
bring everything to 68-70F. 1 Liter glass
bottles (usually full). 6 Liter tub of water.
Well, in typical high-school chemistry fashion:
Neglecting the thermal effects of the bottles
Assuming everything is in a perfectly insulating container
Aq + Br + Cs = T * (A + B + C)
A, B, C ... are the volumes
q, r, s ... are their initial temperatures
T is the final temperature
Which should be sort of obvious, if you
think about it.
For a bottle (vol. A, temp q) in a water bath
(vol. B, temp r), the temperature r at the start to
reach a final temperature T should be
r = [(A / B) * (T - q)] + T
or: r = [(the ratio of the volumes)
times
(the difference in temperatures)]
plus
the final temperature
Not a bad thing to tape to the wall.
For one bottle:
The volume ratio is 1:6
The temperature difference is 68F - 62F = 6F
The final temperature is to be 68F
r = 1/6 * 6F + 68F
= 70F water bath
For 3 bottles the volume ratio is 3:6,
the student can calculate the temperature.
Quiz next Tuesday.
In real life things will be different: you have a flow of
heat to the air, the water bath container, the lab bench,
the glass bottle, and you are loosing heat to evaporation,
gaining heat from your stirring, loosing heat to warming
the chemicals in the bottle (don't forget to use the
volume of the water _before_ the chemicals were mixed in)...
Experiment and making a table will be the fastest and
most accurate method. Which is also sort of obvious.
==
Nicholas O. Lindan
Cleveland Engineering Design, LLC
Cleveland, Ohio 44121
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