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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: ferris on December 12, 2017, 11:04:58 AM

Title: Specific heat capacity for 50% of ethanol water mixture
Post by: ferris on December 12, 2017, 11:04:58 AM

Hello, can somebody tell me the specific heat capacity for 50% ethanol water mixture? Need to put in this information in my thesis, please give me a reliable reference link if possible. Thank you so much

Title: Re: Specific heat capacity for 50% of ethanol water mixture
Post by: Enthalpy on December 13, 2017, 07:32:25 PM

Welcome, ferris!

http://www.ddbst.com/en/EED/CPE/CPE0%20Ethanol%3BWater.php

Title: Re: Specific heat capacity for 50% of ethanol water mixture
Post by: XeLa. on December 13, 2017, 07:50:47 PM

Out of curiosity, does the heat capacity of a mixture follow any sort of estimable expression, possibly described given the specific heat capacities of the pure compounds, as well as the molar fraction? I tried plotting the data given by Enthalpy, and it appeared to follow a second-order polynomial increase, followed by a rough linear regression. Would the trend more so pertain to the interaction between molecular at the molecular scale?

I was just interested.

Title: Re: Specific heat capacity for 50% of ethanol water mixture
Post by: Enthalpy on December 14, 2017, 08:58:00 AM

For simple mixtures and estimates 2% accurate, I would just add the heat capacities of the component amounts.

Only because ethanol+water is knowingly abnormal (the water and ethanol volumes don't add), and because ferris expressly asked, did I look for better data.

Note that the table is only a correction to the linear interpolation. And I have no opinion whatsoever about how to estimate such a correction.

Title: Re: Specific heat capacity for 50% of ethanol water mixture
Post by: XeLa. on December 16, 2017, 09:06:02 AM

Okay, thanks Enthalpy! I guess since the two are miscible in each other, then you wouldn't expect to add 25 mL of one and 50 mL of the other, and achieve a 75 mL solution. That makes sense! I'll have to look at it more in my own time.

Title: Re: Specific heat capacity for 50% of ethanol water mixture
Post by: Borek on December 16, 2017, 10:38:01 AM

Not exactly - 25.0 mL EtOH + 50.0 mL of water yields 72.8mL, 50.0 mL EtOH + 25.0 mL of water yields 72.5 mL. That's assuming anhydrous EtOH.