Английская Википедия:Acid salt
Шаблон:Short description Шаблон:Use dmy dates Acid salts are a class of salts that produce an acidic solution after being dissolved in a solvent. Its formation as a substance has a greater electrical conductivity than that of the pure solvent.[1] An acidic solution formed by acid salt is made during partial neutralization of diprotic or polyprotic acids. A half-neutralization occurs due to the remaining of replaceable hydrogen atoms from the partial dissociation of weak acids that have not been reacted with hydroxide ions (Шаблон:Chem2) to create water molecules.
Acidic solution and examples of acid salts
Acid–base property of the resulting solution from a neutralization reaction depends on the remaining salt products. A salt containing reactive cations undergo hydrolysis by which they react with water molecules, causing deprotonation of the conjugate acids.
For example, the acid salt ammonium chloride is the main species formed upon the half neutralization of ammonia in aqueous solution of hydrogen chloride:[2]
Use in food
Acidic salts are often used in foods as part of leavening agents. In this context, the acid salts are referred to as "leavening acids."[9] Common leavening acids include cream of tartar and monocalcium phosphate.
An acidic salt can be mixed with an alkali salt (such as sodium bicarbonate or baking soda) to create baking powders which release carbon dioxide.[10] Leavening agents can be slow-acting (e.g. sodium aluminum phosphate) which react when heated, or fast-acting (e,g, cream of tartar) which react immediately at low temperatures. Double-acting baking powders contain both slow- and fast-acting leavening agents and react at low and high temperatures to provide leavening rising throughout the baking process.[11]
Disodium phosphate, Шаблон:Chem2, is used in foods and monosodium phosphate, Шаблон:Chem2, is used in animal feed, toothpaste and evaporated milk.
Intensity of acid
An acid with higher [[Acid dissociation constant|Шаблон:Mvar]] value dominates the chemical reaction. It serves as a better contributor of protons (Шаблон:Chem2). A comparison between the Шаблон:Mvar and [[Base dissociation constant|Шаблон:Mvar]] indicates the acid–base property of the resulting solution by which:
- The solution is acidic if Шаблон:Math. It contains a greater concentration of Шаблон:Chem2 ions than concentration of Шаблон:Chem2 ions due more extensive of cation hydrolysis compared to that of anion hydrolysis.
- The solution is alkali if Шаблон:Math. Anions hydrolyze more than cations, causing an exceeding concentration of Шаблон:Chem2 ions.
- The solution is expected to be neutral only when Шаблон:Math.[12]
Other possible factors that could vary pH level of a solution are the relevant equilibrium constants and the additional amounts of any base or acid.
For example, in ammonium chloride solution, Шаблон:Chem2 is the main influence for acidic solution. It has greater Шаблон:Mvar value compared to that of water molecules; Шаблон:Mvar of Шаблон:Chem2 is Шаблон:Val, and Шаблон:Mvar of Шаблон:Chem2 is Шаблон:Val. This ensures its deprotonation when reacting with water, and is responsible for the pH below 7 at room temperature. Шаблон:Chem2 will have no affinity for Шаблон:Chem2 nor tendency to hydrolyze, as its Шаблон:Mvar value is very low (Шаблон:Mvar of Шаблон:Chem2 is Шаблон:Val).[13]
Hydrolysis of ammonium at room temperature produces:
- <chem>NH4+_{(aq)}\ + H2O_{(aq)} <=> NH3_{(aq)}\ + H3O+_{(aq)}</chem>
- <math alt="K a can be written as a ratio of three terms. The numerator of the ratio holds the concentration of the deprotonated base N H 3, times that of the hydronium ion H 3 O +. The denominator holds the activity of the acid N H 4 +. Using the definition for K a, K b equals K w divided by K A." >
K_\mathrm{a} = \frac{\mathrm{[NH_3][H_3O^+]}}{\mathrm{[NH_4^+]}} = \frac{K_\mathrm{w}}{K_\mathrm{b}}
</math>
- <math alt="K a can be written as a ratio of two terms. The numerator holds the concentration of 1 . 0 times 1 0 ^ - 1 4. The denominator holds the concentration of 1 . 8 times 1 0 ^ - 5." >
K_\mathrm{a} = \frac{[1.0 \times 10^{-14}]}{[1.8 \times 10^{-5}]} = {5.6} \times 10^{-10}</math>
See also
- Alkali salt
- Salt (chemistry)
- Oxoacid
- Sodium bicarbonate
- Sodium bisulfate
- Disodium phosphate
- Monosodium phosphate
References
- ↑ Шаблон:Cite journal
- ↑ Шаблон:Cite book
- ↑ U.S. Coast Guard, Department of Transportation. CHRIS - Hazardous Chemical Data. Volume II. Washington, D.C.: U.S. Government Printing Office, 1984-5.
- ↑ Lewis, R.J. Sr.; Hawley's Condensed Chemical Dictionary 15th Edition. John Wiley & Sons, Inc. New York, NY 2007., p. 1153
- ↑ Lide, D.R. CRC Handbook of Chemistry and Physics 88TH Edition 2007-2008. CRC Press, Taylor & Francis, Boca Raton, Florida 2007, p. 4-90
- ↑ Haynes, W.M. (ed.). CRC Handbook of Chemistry and Physics. 95th Edition. CRC Press LLC, Boca Raton: FL 2014-2015, p. 4-89
- ↑ Шаблон:Cite journal
- ↑ 8,0 8,1 Шаблон:Cite book
- ↑ Шаблон:Cite web
- ↑ Шаблон:Cite web
- ↑ Шаблон:Cite journal
- ↑ Шаблон:Cite book
- ↑ Lower, S.K., (1999). Introduction to acid-base chemistry. Chem1 General Chemistry Text. Retrieved from http://www.chem1.com/acad/pdf/c1xacid1.pdf
