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Ammonia solution, also known as ammonia water, ammonium hydroxide, ammoniacal liquor, ammonia liquor, aqua ammonia, aqueous ammonia, or (inaccurately) ammonia, is a solution of ammonia in water. It can be denoted by the symbols NH 3 (aq). Although the name ammonium hydroxide suggests a salt with the composition [NH + 4][OH −
The table above gives properties of the vapor–liquid equilibrium of anhydrous ammonia at various temperatures. The second column is vapor pressure in kPa. The third column is the density of the liquid phase. The fourth column is the density of the vapor.
The hazards of ammonia solutions depend on the concentration: 'dilute' ammonia solutions are usually 5–10% by weight (< 5.62 mol/L); 'concentrated' solutions are usually prepared at >25% by weight. A 25% (by weight) solution has a density of 0.907 g/cm 3 , and a solution that has a lower density will be more concentrated.
Specific volumes of pure ammonia under the pressure corresponding to saturation have been determined from -78° to 100° C. The method employed is similar to one previously used by Dieterici, and consists essentially in observing, at various temperatures, the volumes of the liquid and vapour phases in equilibrium in a closed vessel.
The blue colour of the solution is due to ammoniated electrons, which absorb energy in the visible region of light. The diffusivity of the solvated electron in liquid ammonia can be determined using potential-step chronoamperometry. [6] Solvated electrons in ammonia are the anions of salts called electrides. Na + 6 NH 3 → [Na(NH 3) 6] + + e −
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Thus, the treatment of concentrated solutions of ammonium salts with a strong base gives ammonia. When ammonia is dissolved in water, a tiny amount of it converts to ammonium ions: H 2 O + NH 3 ⇌ OH − + [NH 4] + The degree to which ammonia forms the ammonium ion depends on the pH of the solution. If the pH is low, the equilibrium shifts to ...
For example, the limiting acid in liquid ammonia is the ammonium ion, NH 4 + which has a pK a value in water of 9.25. The limiting base is the amide ion, NH 2 −. NH 2 − is a stronger base than the hydroxide ion and so cannot exist in aqueous solution. The pK a value of ammonia is estimated to be approximately 34 (c.f. water, 14 [3] [4]).