What is the pH Level of Urea & Sweat?

[xLaser]

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.

 

[tyco05]

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.

 

[primarygun]

Urea reacts with water to form ammonium ions and carbonate ions.
Indeed alkaline.

 

[sandipmsu]

pH of ammonia is near about 9.5.

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

 

[Borek]

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:

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.

 

[chemisttree]

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!