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In aqueous solution, ammonia deprotonates a small fraction of the water to give ammonium and hydroxide according to the following equilibrium: . NH 3 + H 2 O ⇌ NH + 4 + OH −.. In a 1 M ammonia solution, about 0.42% of the ammonia is converted to ammonium, equivalent to pH = 11.63 because [NH +
Heating at higher temperatures results in decomposition into ammonia, nitrogen, sulfur dioxide, and water. [17] As a salt of a strong acid (H 2 SO 4) and weak base (NH 3), its solution is acidic; the pH of 0.1 M solution is 5.5. In aqueous solution the reactions are those of NH + 4 and SO 2−
By accounting for the self-ionization of water, the true pH of the solution can be calculated. For example, a 5×10 −8 M solution of HCl would have a pH of 6.89 when treated as a mixture of HCl and water. The self-ionization equilibrium of solutions of sodium hydroxide at higher concentrations must also be considered.
The toxicity of ammonia is dependent on both pH and temperature and an added complexity is the buffering effect of the blood/water interface across the gill membrane which masks any additional toxicity over about pH 8.0. The management of river chemistry to avoid ecological damage is particularly difficult in the case of ammonia as a wide range ...
The Henderson–Hasselbalch equation can be used to model these equilibria. It is important to maintain this pH of 7.4 to ensure enzymes are able to work optimally. [10] Life threatening Acidosis (a low blood pH resulting in nausea, headaches, and even coma, and convulsions) is due to a lack of functioning of enzymes at a low pH. [10]
Ammonia readily dissolves in water. In an aqueous solution, it can be expelled by boiling. The aqueous solution of ammonia is basic, and may be described as aqueous ammonia or ammonium hydroxide. [30] The maximum concentration of ammonia in water (a saturated solution) has a specific gravity of 0.880 and is often known as '.880 ammonia'. [31]
The pH of such a solution is close to a value of 7; the exact pH value is dependent on the temperature of the solution. Neutralization is an exothermic reaction. The standard enthalpy change for the reaction H + + OH − → H 2 O is −57.30 kJ/mol.
Buffer capacity falls to 33% of the maximum value at pH = pK a ± 1, to 10% at pH = pK a ± 1.5 and to 1% at pH = pK a ± 2. For this reason the most useful range is approximately p K a ± 1. When choosing a buffer for use at a specific pH, it should have a p K a value as close as possible to that pH.