37.8g of water to give a freezing point of -.15 degrees C

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Discussion Overview

The discussion revolves around a chemistry homework problem involving the calculation of how many grams of ethyl alcohol must be added to 37.8g of water to achieve a freezing point of -0.15 degrees Celsius. The scope includes theoretical aspects of freezing point depression and practical considerations for experimental determination.

Discussion Character

  • Homework-related
  • Technical explanation
  • Exploratory

Main Points Raised

  • One participant requests assistance with a chemistry homework problem regarding the addition of ethyl alcohol to water to lower its freezing point.
  • Another participant suggests that determining the freezing point experimentally may be challenging and raises a question about the potential turbidity of the solution at the freezing point.
  • A different participant mentions the importance of the cryoscopic constant and inquires about its value for water, as well as the required molality of ethanol.
  • One participant cautions to ensure that the correct substance is being referenced, noting the difference between ethyl alcohol and ethylene glycol, as they have different molecular weights affecting the calculations.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus on the specifics of the calculation or the experimental approach, indicating that multiple competing views and uncertainties remain in the discussion.

Contextual Notes

There is a lack of clarity regarding the cryoscopic constant for water and the specific molality needed for the freezing point depression calculation. Additionally, the distinction between ethyl alcohol and ethylene glycol introduces potential confusion in the problem-solving process.

trixie23
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Hey, I really need help in my chem homework. :(

how many grams of ethyl alcohol CH2OHCH2OH must be added to 37.8g of water to give a freezing point of -.15 degrees C.
 
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One must either find this information in a handbook or conduct a determination experimentally. I may suspect that doing the determination experimentally could be difficult, since freezing of a liquid is being watched for. Anybody have a guess, would the solution turn turbid near or at the freezing point? One would want to gently agitate the solution during cooling to uniformly distribute the temperatures.
 


I guess it is just about cryoscopic constant. What is cryoscopic constant for water? What molality of ethanol do you need?
 


Once you have the molality, check you don't mean ethane-1,2-diol, (ethylene glycol), rather than ethanol - the two have different molecular weights, and so will generate different masses...
 

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