In common usage, the term “ammonia” generally refers to the cleaning solutions purchased at retail stores. Pure ammonia (chemical formula NH3, commonly called “anhydrous ammonia”) is actually a gas at room temperature. Anhydrous ammonia will readily dissolve in water to form ammonium hydroxide (chemical formula NH?OH, sometimes called “ammonia water” or \"aqua ammonia\"), and these are the solutions sold as cleaning agents.
Household ammonia is typically 2 percent to 10 percent by weight. This means that 100 g of ammonia solution would actually contain only 2 grams to 10 grams of actual ammonia.
Density is the ratio between a substance’s mass and the volume of space it occupies. The density of pure water at room temperature is 1.00 g per milliliter (g/mL). Dilute ammonia solutions (2 to 3 percent ammonia) have densities of about 0.980 g/mL, whereas more concentrated (10 percent) ammonia solutions have densities of about 0.975 g/mL. In general, the more ammonia in the solution, the lower the solution’s density.
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Concentrated ammonia solutions (10 percent) have freezing points of about 18 degrees Fahrenheit, versus 32 degrees Fahrenheit for pure water. The more dilute the solution, the closer the freezing point will be to 32 degrees Fahrenheit. Thus, a 2 percent ammonia solution has a freezing point near 32 degrees Fahrenheit.
Water boils at 212 degrees Fahrenheit, and dilute (2 percent) ammonia solutions will boil within a few degrees of this temperature. Concentrated (10 percent) ammonia solutions, however, have boiling points of about 145 degrees Fahrenheit. In general, the higher the ammonia content, the lower the boiling point.
The measurement of the acidity or basicity of a water-based solution is pH. Values less than 7 indicate an acidic solution, whereas values above 7 indicate a basic solution. A pH of exactly 7 is considered neutral. A 2 percent ammonia solution exhibits a pH of 11.2 to 11.8, whereas a 10 percent solution exhibits a pH of about 12. In general, the higher the concentration of ammonia, the higher the pH.