I was just curious. Due to the basic nature of potassium nitrate, and the acidic nature of ammonium nitrate, would mixing the two nitrate salts cause
them to decompose slowly over long periods of time?BromicAcid - 29-6-2004 at 15:40
Potassium nitrate solutions are actually slightly acidic, a 40% solution in water has a pH of 6.5 which is only very very slightly acidic as you know.
I guess I was just thrown off because potassium is an alkaline metal.Pyrovus - 29-6-2004 at 21:50
NH4NO3 will slowly decompose on it's own, as a result of the equilibrium:
NH4+ <-> NH3 + H+
Though this equilibrium lies to the left, some of the ammonia formed will escape into the atmosphere, so the system will be continually losing
ammonia.
There also exists the equilibrium:
H+ + NO3- <-> HNO3
Which although this too lies predominately to the left, it to a small extent helps to hinder the reverse reaction of the first equilibrium by removing
some of the protons formed. Adding KNO3 provides more nitrate ions, which will increase the number of protons removed by the second equilibrium.
So the net effect should be that KNO3 should act as a catalyst (albeit not a very good one) for the
decomposition of ammonium nitrate into ammonia and nitric acid.
[Edited on 30-6-2004 by Pyrovus]Darkfire - 29-6-2004 at 22:16
Quote:
Originally posted by tom haggen
I guess I was just thrown off because potassium is an alkaline metal.
Yes, the K ions like to seperate
fully from the NO3 ions as well as not changing the waters ph. But the same is true for the NO3 ions in relations to the K ions and the water thus the
pH is close to 7.
This is becuase both the K ions and NO3 ions are both "strong". If it was a compound like NH4Cl or KCOOH you would expect a greater pH
change.
