[pure-silver] Re: Basic Chemistry
- From: "Peter Badcock" <peter.badcock@xxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Sun, 15 Jun 2008 21:20:03 +1000
Slight error in my post - only degF is scaled and offset, whereas degC is
just offset (relative to absolute zero)
Peter
2008/6/15 Peter Badcock <peter.badcock@xxxxxxxxx>:
> Nicholas,
>
> Should T not be expressed in degrees Kelvin rather than degF ? This then
> takes into account the absolute nature of the temps in the system, rather
> than a temperature that has been scaled and offset (as are degF and degC).
>
> Peter
>
> 2008/6/13 Nicholas O. Lindan <nolindan@xxxxxxxxxxxxx>:
>
> <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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>
>
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