Why Does Heat Generate When Mixing Ethanol and Water?

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    Ethanol Mixing Water
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Discussion Overview

The discussion centers on the thermodynamic phenomenon of heat generation when mixing ethanol and water, exploring the underlying molecular interactions and bond dynamics involved in the process. Participants examine the exothermic nature of the mixing and the implications of hydrogen bond formation and breaking.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant inquires about the reason heat is generated when ethanol is mixed with water and questions the disintegration of existing hydrogen bonds in water to accommodate ethanol.
  • Another participant suggests that the smaller size of ethanol molecules allows them to fit between water molecules, leading to the breaking of hydrogen bonds and resulting in an exothermic enthalpy of mixing.
  • A correction is made regarding the relative sizes of water and ethanol molecules, with an acknowledgment that the initial claim was incorrect.
  • A participant questions why the mixing is exothermic if hydrogen bonds are reformed after breaking, suggesting that the energy dynamics of bond strength must be considered.
  • Another participant proposes that the heat liberation may be due to the weaker hydrogen bonds formed between water and ethanol compared to the original water-water bonds.
  • A request is made for clarification on how the difference in bond strength is measured.

Areas of Agreement / Disagreement

Participants express differing views on the molecular interactions at play and the reasons for the exothermic nature of the mixing. The discussion remains unresolved regarding the precise mechanisms and measurements of bond strength differences.

Contextual Notes

Participants have not reached a consensus on the explanation for the exothermic reaction, and there are unresolved questions regarding the measurement of bond strength differences.

Who May Find This Useful

This discussion may be of interest to those studying thermodynamics, molecular chemistry, or anyone curious about the interactions between solvents and solutes in mixtures.

nirmaljoshi
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Why heat is generated when ethanol is mixed with water? Please also explain why the existing hydrogen bond of water disintegrated to accommodate ethanol molecule?
 
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Ethanol molecules are much smaller in size than the water molecules and as a consequence some of the ethanol molecules tend to cram in between the water molecules, thus breaking the hydrogen bond.
Enthalpy of mixing water and ethanol is -ve(exothermic), hence heat is liberated.
 
sagarbhathwar said:
Ethanol molecules are much smaller in size than the water molecules and as a consequence some of the ethanol molecules tend to cram in between the water molecules, thus breaking the hydrogen bond.

Water molecules are significantly smaller than ethanol molecules.

Water: H2O
Ethanol: CH3-CH2-OH
 
Oh I am extremely sorry. It exactly the other way around. Swap places with ethanol and water :)

Thanks
Sagar
 
sagarbhathwar said:
Enthalpy of mixing water and ethanol is -ve(exothermic), hence heat is liberated.

My question is why it is exothermic? As you said, "Ethanol molecules are much smaller in size than the water molecules and as a consequence some of the ethanol molecules tend to cram in between the water molecules, thus breaking the hydrogen bond."

But after mixing, water and ethanol again forms the hydrogen bond and hence they remain in stable form. That is, one hydrogen bond is broken and another is formed. If so, there should not be any liberation of energy.

Please correct me if i am on wrong way.
 
Yes. H-bond is formed again between hydrogen and water molecules but the strength of this bond is weaker than that between water-water molecules. So I am guessing that is why some heat is liberated.
Always consider difference in strength of the bonds. Not just the bonds.
 
Thanks.

Could you please briefly direct me how the difference in strength of bond is measured?
 

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