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Concept
Ammonia solution
Summary
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 NH3(aq). Although the name ammonium hydroxide suggests an alkali with the composition [NH4+][OH-], it is actually impossible to isolate samples of NH4OH. The ions NH4+ and OH− do not account for a significant fraction of the total amount of ammonia except in extremely dilute solutions.
In aqueous solution, ammonia deprotonates a small fraction of the water to give ammonium and hydroxide according to the following equilibrium:
NH3 + H2O NH4+ + OH−.
In a 1 M ammonia solution, about 0.42% of the ammonia is converted to ammonium, equivalent to pH = 11.63
because [NH4+] = 0.0042 M, [OH−] = 0.0042 M, [NH3] = 0.9958 M, and pH = 14 + log10[OH−] = 11.62. The base ionization constant is
Kb = [NH4+][OH−]/[NH3] = 1.77.
Like other gases, ammonia exhibits decreasing solubility in solvent liquids as the temperature of the solvent increases. Ammonia solutions decrease in density as the concentration of dissolved ammonia increases. At , the density of a saturated solution is 0.88 g/ml and contains 35.6% ammonia by mass, 308 grams of ammonia per litre of solution, and has a molarity of approximately 18 mol/L. At higher temperatures, the molarity of the saturated solution decreases and the density increases. Upon warming of saturated solutions, ammonia gas is released.
In contrast to anhydrous ammonia, aqueous ammonia finds few non-niche uses outside of cleaning agents.
Diluted (1–3%) ammonia is also an ingredient of numerous cleaning agents, including many window cleaning formulas. Because aqueous ammonia is a gas dissolved in water, as the water evaporates from a window, the gas evaporates also, leaving the window streak-free.
In addition to use as an ingredient in cleansers with other cleansing ingredients, ammonia in water is also sold as a cleaning agent by itself, usually labeled as simply "ammonia".
Official source
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