What is the pH Level of Urea & Sweat?

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Discussion Overview

The discussion centers around the pH levels of urea and sweat, exploring the chemical properties of urea, its reactions in solution, and the factors influencing the pH of sweat. Participants examine the basicity of ammonia and its implications for the pH of related substances.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant inquires about the pH level of urea and sweat, suggesting both may be basic due to ammonia content.
  • Another participant clarifies that ammonia (NH3) is a weak base and discusses the conditions under which it may exhibit acidic properties.
  • A different participant states that urea reacts with water to produce ammonium and carbonate ions, indicating it is alkaline.
  • One post emphasizes that the pH of urea is not a fixed value but depends on the concentration of urea in solution, and similarly for sweat, which varies based on diet and health.
  • A participant provides a specific pH value for a 10% urea solution, citing a reference, and discusses the chemical reactions that occur upon heating urea.

Areas of Agreement / Disagreement

Participants express differing views on the nature of urea and its pH, with some asserting it is alkaline while others emphasize the dependency on concentration and context. There is no consensus on the exact pH values or the implications of urea's reactions.

Contextual Notes

Limitations include the lack of consensus on the pH of urea and sweat, the dependency of pH on concentration, and the variability of sweat composition based on individual factors.

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Urea? pH level of it?

Does anyone know the pH level of Urea or Sweat? I can't seem to find this info anywhere, although I think both is basic since they contain ammonia.
 
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Isn't ammonia NH3 ?? And hence would more likely be acidic (as basic requires OH- ions). Also, it would only be acidic if H+ ions dissociated from the ammonia, which can happen. I'm not sure what else is in sweat... but that's my two cents...
Don't forget that pH is also a measure of concentration, so you would need to know what the concentration of urea in your samples is.

OK... just found a website that is probably going to get you as far as you can

http://en.wikipedia.org/wiki/Urea

it should be some help.
 
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Urea reacts with water to form ammonium ions and carbonate ions.
Indeed alkaline.
 





pH of ammonia is near about 9.5.

Its basicity is due to the generation of NH4+ ion in the Aquas soln...
 


Not only this is not physics, but none of the answers given so far is correct...

No such thing as pH of urea. If anything, there is pH of urea solution - and it depends on the urea concentration. Same holds for every acid/base, weak and strong.

I feel like the OP asks about pH of URINE and sweat. These are variable and depend on the diet and health condition.

Now, ammonia is NH3 - that's correct. Its solutions are basic, bacause it reacts with water generating OH-:

NH3 + H2O <-> NH4+ + OH-

Equilibrium constant for this reaction is about 1.8*10-5 - so ammonia is a weak base. Brønsted-Lowry's base to be precise. See pH calculation lectures for more details.

I don't have exact data for urea at hand, but its solutions are slightly alkaline as well - for the same reason, urea is a Brønsted-Lowry's base and reacts with water.

However, reaction of urea with water mentioned by primarygun:

primarygun said:
Urea reacts with water to form ammonium ions and carbonate ions.

is different. That's hydrolyzis that decomposes urea, so the solution is no longer solution of urea.
 
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A 10% solution of urea yields a pH of about 7.2 (Merck Index, 11th Ed., p. 9789). It develops an odor of NH3 (which is actually NH3, BTW) as a solid. Upon heating it forms biuret and ammonia. Further heating yields cyanuric acid.

2 NH2CONH2 -------> NH2CONHCONH2 (biuret) + NH3

According to Merck the above reaction won't occur unless urea is heated to above its melting point, but if you look carefully at reagent grade material, you will notice that it is a prill. A prill is formed by melting something and dropping it from a height sufficient for it to cool to a solid before it lands on the ground. Thus all reagent grade urea tests positive for biuret.

Please don't necropost! This thread is over 4 years old!
 

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