Acid salt

Last updated January 02, 2024

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 (OH⁻) 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]

NH₃(aq) + HCl(aq) → [NH₄]⁺Cl⁻(aq)

Example of acid salts
Name	Sodium bisulfate	Monosodium phosphate	Disodium phosphate
Structural formula
Chemical formula	NaHSO₄	NaH₂PO₄	Na₂HPO₄
IUPAC name	Sodium hydrogen sulfate	Sodium dihydrogen phosphate	Disodium hydrogen phosphate
Other name	Sodium acid sulfate Bisulfate of soda	Monobasic sodium phosphate Sodium acid phosphate Sodium biphosphate	Disodium hydrogen orthophosphate Sodium phosphate dibasic disodium phosphate
Molecular weight	120.054 g/mol	119.976 g/mol	141.957 g/mol
Formal charge	zero	zero	zero
Odour	Odourless	Odourless	Odourless^[3]
Appearance	White crystals or granules	White crystalline powder^[4]	White, hygroscopic powder^[5]
Structure	triclinic (anhydrous) monoclinic (monohydrate)	Monoclinic crystals^[6]	Monoclinic crystals (anhydrous)^[7]
Solubility	Soluble in water Insoluble in ammonia	Soluble in water Insoluble in ethanol or ether	Soluble in water Insoluble in ethanol
Density	2.742 g/cm³ (anhydrous) 1.8 g/cm³ (monohydrate)	0.5–1.2 g/cm³	1.7 g/cm³
Decomposition (through heating)		Emits toxic fumes of phosphoxides and sodium oxide^[8]	Emits toxic fumes of phosphorus- and sodium oxides^[8]
Uses	Bleaching agents Plating agents and surface treating agents Cleaning and Furnishing Care Products	Treat constipation Clean the bowel before a colonoscopy Bleaching agents	A source of phosphorus Visicol tablets are indicated for cleansing of the colon Corrosion inhibitors and anti-scaling agents

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, Na₂HPO₄, is used in foods and monosodium phosphate, NaH₂PO₄, is used in animal feed, toothpaste and evaporated milk.

Intensity of acid

An acid with higher $K a$ value dominates the chemical reaction. It serves as a better contributor of protons (H⁺). A comparison between the $K a$ and $K b$ indicates the acid–base property of the resulting solution by which:

The solution is acidic if $K a > K b$ . It contains a greater concentration of H⁺ ions than concentration of OH⁻ ions due more extensive of cation hydrolysis compared to that of anion hydrolysis.
The solution is alkali if $K a < K b$ . Anions hydrolyze more than cations, causing an exceeding concentration of OH⁻ ions.
The solution is expected to be neutral only when $K a = K b$ .^[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, NH+4 is the main influence for acidic solution. It has greater $K a$ value compared to that of water molecules; $K a$ of NH+4 is 5.6×10⁻¹⁰, and $K w$ of H₂O is 1.0×10⁻¹⁴. This ensures its deprotonation when reacting with water, and is responsible for the pH below 7 at room temperature. Cl⁻ will have no affinity for H⁺ nor tendency to hydrolyze, as its $K b$ value is very low ( $K b$ of Cl⁻ is 7.7×10⁻²¹).^[13]

Hydrolysis of ammonium at room temperature produces:

{\ce {NH4+_{(aq)}\ + H2O_{(aq)}<=> NH3_{(aq)}\ + H3O+_{(aq)}}}

K_{\mathrm {a} }={\frac {\mathrm {[NH_{3}][H_{3}O^{+}]} }{\mathrm {[NH_{4}^{+}]} }}={\frac {K_{\mathrm {w} }}{K_{\mathrm {b} }}}

K_{\mathrm {a} }={\frac {[1.0\times 10^{-14}]}{[1.8\times 10^{-5}]}}={5.6}\times 10^{-10}

Related Research Articles

An acid is a molecule or ion capable of either donating a proton (i.e. hydrogen ion, H⁺), known as a Brønsted–Lowry acid, or forming a covalent bond with an electron pair, known as a Lewis acid.

In chemistry, an acid–base reaction is a chemical reaction that occurs between an acid and a base. It can be used to determine pH via titration. Several theoretical frameworks provide alternative conceptions of the reaction mechanisms and their application in solving related problems; these are called the acid–base theories, for example, Brønsted–Lowry acid–base theory.

Hydroxide is a diatomic anion with chemical formula OH⁻. It consists of an oxygen and hydrogen atom held together by a single covalent bond, and carries a negative electric charge. It is an important but usually minor constituent of water. It functions as a base, a ligand, a nucleophile, and a catalyst. The hydroxide ion forms salts, some of which dissociate in aqueous solution, liberating solvated hydroxide ions. Sodium hydroxide is a multi-million-ton per annum commodity chemical. The corresponding electrically neutral compound HO^• is the hydroxyl radical. The corresponding covalently bound group –OH of atoms is the hydroxy group. Both the hydroxide ion and hydroxy group are nucleophiles and can act as catalysts in organic chemistry.

Hydrolysis is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile.

In chemistry, a salt is a chemical compound consisting of an ionic assembly of positively charged cations and negatively charged anions, which results in a compound with no net electric charge. A common example is table salt, with positively charged sodium ions and negatively charged chloride ions.

In chemistry, an acid dissociation constant is a quantitative measure of the strength of an acid in solution. It is the equilibrium constant for a chemical reaction

Solubility equilibrium is a type of dynamic equilibrium that exists when a chemical compound in the solid state is in chemical equilibrium with a solution of that compound. The solid may dissolve unchanged, with dissociation, or with chemical reaction with another constituent of the solution, such as acid or alkali. Each solubility equilibrium is characterized by a temperature-dependent solubility product which functions like an equilibrium constant. Solubility equilibria are important in pharmaceutical, environmental and many other scenarios.

<span class="mw-page-title-main">Ammonium</span> Chemical compound

The ammonium cation is a positively charged polyatomic ion with the chemical formula NH+4 or [NH₄]⁺. It is formed by the protonation of ammonia. Ammonium is also a general name for positively charged (protonated) substituted amines and quaternary ammonium cations, where one or more hydrogen atoms are replaced by organic or other groups.

In chemistry, pyrophosphates are phosphorus oxyanions that contain two phosphorus atoms in a P−O−P linkage. A number of pyrophosphate salts exist, such as disodium pyrophosphate and tetrasodium pyrophosphate, among others. Often pyrophosphates are called diphosphates. The parent pyrophosphates are derived from partial or complete neutralization of pyrophosphoric acid. The pyrophosphate bond is also sometimes referred to as a phosphoanhydride bond, a naming convention which emphasizes the loss of water that occurs when two phosphates form a new P−O−P bond, and which mirrors the nomenclature for anhydrides of carboxylic acids. Pyrophosphates are found in ATP and other nucleotide triphosphates, which are important in biochemistry. The term pyrophosphate is also the name of esters formed by the condensation of a phosphorylated biological compound with inorganic phosphate, as for dimethylallyl pyrophosphate. This bond is also referred to as a high-energy phosphate bond.

In chemistry, there are three definitions in common use of the word "base": Arrhenius bases, Brønsted bases, and Lewis bases. All definitions agree that bases are substances that react with acids, as originally proposed by G.-F. Rouelle in the mid-18th century.

<span class="mw-page-title-main">Sodium bicarbonate</span> Chemical compound

Sodium bicarbonate (IUPAC name: sodium hydrogencarbonate), commonly known as baking soda or bicarbonate of soda, is a chemical compound with the formula NaHCO₃. It is a salt composed of a sodium cation (Na⁺) and a bicarbonate anion (HCO₃⁻). Sodium bicarbonate is a white solid that is crystalline, but often appears as a fine powder. It has a slightly salty, alkaline taste resembling that of washing soda (sodium carbonate). The natural mineral form is nahcolite. It is a component of the mineral natron and is found dissolved in many mineral springs.

<span class="mw-page-title-main">Baking powder</span> Dry chemical leavening agent

Baking powder is a dry chemical leavening agent, a mixture of a carbonate or bicarbonate and a weak acid. The base and acid are prevented from reacting prematurely by the inclusion of a buffer such as cornstarch. Baking powder is used to increase the volume and lighten the texture of baked goods. It works by releasing carbon dioxide gas into a batter or dough through an acid–base reaction, causing bubbles in the wet mixture to expand and thus leavening the mixture. The first single-acting baking powder was developed by food manufacturer Alfred Bird in England in 1843. The first double-acting baking powder, which releases some carbon dioxide when dampened and later releases more of the gas when heated by baking, was developed by Eben Norton Horsford in the U.S. in the 1860s.

In cooking, a leavening agent or raising agent, also called a leaven or leavener, is any one of a number of substances used in doughs and batters that cause a foaming action that lightens and softens the mixture. An alternative or supplement to leavening agents is mechanical action by which air is incorporated. Leavening agents can be biological or synthetic chemical compounds. The gas produced is often carbon dioxide, or occasionally hydrogen.

In chemistry, the common-ion effect refers to the decrease in solubility of an ionic precipitate by the addition to the solution of a soluble compound with an ion in common with the precipitate. This behaviour is a consequence of Le Chatelier's principle for the equilibrium reaction of the ionic association/dissociation. The effect is commonly seen as an effect on the solubility of salts and other weak electrolytes. Adding an additional amount of one of the ions of the salt generally leads to increased precipitation of the salt, which reduces the concentration of both ions of the salt until the solubility equilibrium is reached. The effect is based on the fact that both the original salt and the other added chemical have one ion in common with each other.

<span class="mw-page-title-main">Neutralization (chemistry)</span> Chemical reaction in which an acid and a base react quantitatively

In chemistry, neutralization or neutralisation is a chemical reaction in which acid and a base react with an equivalent quantity of each other. In a reaction in water, neutralization results in there being no excess of hydrogen or hydroxide ions present in the solution. The pH of the neutralized solution depends on the acid strength of the reactants.

<span class="mw-page-title-main">Barium hydroxide</span> Chemical compound

Barium hydroxide is a chemical compound with the chemical formula Ba(OH)₂. The monohydrate (x = 1), known as baryta or baryta-water, is one of the principal compounds of barium. This white granular monohydrate is the usual commercial form.

<span class="mw-page-title-main">Potassium bitartrate</span> Chemical salt used in cooking as cream of tartar

Potassium bitartrate, also known as potassium hydrogen tartrate, with formula KC₄H₅O₆, is a chemical compound with a number of uses, including:

Monocalcium phosphate is an inorganic compound with the chemical formula Ca(H₂PO₄)₂ ("AMCP" or "CMP-A" for anhydrous monocalcium phosphate). It is commonly found as the monohydrate ("MCP" or "MCP-M"), Ca(H₂PO₄)₂·H₂O. Both salts are colourless solids. They are used mainly as superphosphate fertilizers and are also popular leavening agents.

Disodium pyrophosphate or sodium acid pyrophosphate (SAPP) is an inorganic compound with the chemical formula Na₂H₂P₂O₇. It consists of sodium cations (Na⁺) and dihydrogen pyrophosphate anions (H₂P₂O2−7). It is a white, water-soluble solid that serves as a buffering and chelating agent, with many applications in the food industry. When crystallized from water, it forms a hexahydrate, but it dehydrates above room temperature. Pyrophosphate is a polyvalent anion with a high affinity for polyvalent cations, e.g. Ca²⁺.

Monosodium phosphate (MSP), also known as monobasic sodium phosphate and sodium dihydrogen phosphate, is an inorganic compound with the chemical formula NaH₂PO₄. It is a sodium salt of phosphoric acid. It consists of sodium cations (Na⁺) and dihydrogen phosphate anions (H₂PO−4). One of many sodium phosphates, it is a common industrial chemical. The salt exists in an anhydrous form, as well as monohydrate and dihydrate (NaH₂PO₄·H₂O and NaH₂PO₄·2H₂O respectively).

References

↑ Cady, H. P.; Elsey, H. M. (1928). "A general definition of acids, bases, and salts". Journal of Chemical Education. 5 (11): 1425. Bibcode:1928JChEd...5.1425C. doi:10.1021/ed005p1425.
↑ Dekock, Roger L.; Gray, Harry B. (1989). Chemical bonding and structure (Second ed.). Sausalito, California: University Science Book. pp. 97–98. ISBN 978-0-935702-61-3 . Retrieved 8 February 2018.
↑ 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
↑ Somov, N.V.; Chausov, F.F.; Russ, J. (2017). "High-symmetry polymorph of anhydrous disodium hydrogen phosphate". Russian Journal of Inorganic Chemistry. 62 (2): 172–174. doi:10.1134/S0036023617020176. S2CID 102468247.
1 2 Wiley, John; Hoboken, NJ (2004). Sax's Dangerous Properties of Industrial Materials (11th Edition By Richard J. Lewis ed.). Wiley-Interscience. p. 3274. doi:10.1021/ja041002c. ISBN 978-0-471-47662-7.
↑ Wallace, David (10 June 2015). "Leavening Acids – Baking Ingredients". BAKERpedia. Retrieved 17 October 2019.
↑ "The Many Uses of Cream of Tartar". Office for Science and Society. Retrieved 17 October 2019.
↑ Gabriala, Pop (2007). "RESEARCHES REGARDING THE CHEMICAL LEAVENING AGENTS' ROLE IN QUALITY OF BAKERY PRODUCTS". Journal of Agroalimentary Processes and Technologies. XIII, No. 1: 105–112. S2CID 54052197.
↑ Raymond, Chang (2010). Chemistry (tenth ed.). Americas, New York: McGraw-Hill. pp. 725–727. ISBN 978-0077274313 . Retrieved 9 February 2018.
↑ Lower, S.K., (1999). Introduction to acid-base chemistry. Chem1 General Chemistry Text. Retrieved from http://www.chem1.com/acad/pdf/c1xacid1.pdf

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[1] Cady, H. P.; Elsey, H. M. (1928). "A general definition of acids, bases, and salts". Journal of Chemical Education. 5 (11): 1425. Bibcode:1928JChEd...5.1425C. doi:10.1021/ed005p1425.

[2] Dekock, Roger L.; Gray, Harry B. (1989). Chemical bonding and structure (Second ed.). Sausalito, California: University Science Book. pp. 97–98. ISBN 978-0-935702-61-3 . Retrieved 8 February 2018.

[3] U.S. Coast Guard, Department of Transportation. CHRIS - Hazardous Chemical Data. Volume II. Washington, D.C.: U.S. Government Printing Office, 1984-5.

[4] Lewis, R.J. Sr.; Hawley's Condensed Chemical Dictionary 15th Edition. John Wiley & Sons, Inc. New York, NY 2007., p. 1153

[5] Lide, D.R. CRC Handbook of Chemistry and Physics 88TH Edition 2007-2008. CRC Press, Taylor & Francis, Boca Raton, Florida 2007, p. 4-90

[6] Haynes, W.M. (ed.). CRC Handbook of Chemistry and Physics. 95th Edition. CRC Press LLC, Boca Raton: FL 2014-2015, p. 4-89

[7] Somov, N.V.; Chausov, F.F.; Russ, J. (2017). "High-symmetry polymorph of anhydrous disodium hydrogen phosphate". Russian Journal of Inorganic Chemistry. 62 (2): 172–174. doi:10.1134/S0036023617020176. S2CID 102468247.

[:13-8] 1 2 Wiley, John; Hoboken, NJ (2004). Sax's Dangerous Properties of Industrial Materials (11th Edition By Richard J. Lewis ed.). Wiley-Interscience. p. 3274. doi:10.1021/ja041002c. ISBN 978-0-471-47662-7.

[9] Wallace, David (10 June 2015). "Leavening Acids – Baking Ingredients". BAKERpedia. Retrieved 17 October 2019.

[10] "The Many Uses of Cream of Tartar". Office for Science and Society. Retrieved 17 October 2019.

[11] Gabriala, Pop (2007). "RESEARCHES REGARDING THE CHEMICAL LEAVENING AGENTS' ROLE IN QUALITY OF BAKERY PRODUCTS". Journal of Agroalimentary Processes and Technologies. XIII, No. 1: 105–112. S2CID 54052197.

[12] Raymond, Chang (2010). Chemistry (tenth ed.). Americas, New York: McGraw-Hill. pp. 725–727. ISBN 978-0077274313 . Retrieved 9 February 2018.

[13] Lower, S.K., (1999). Introduction to acid-base chemistry. Chem1 General Chemistry Text. Retrieved from http://www.chem1.com/acad/pdf/c1xacid1.pdf

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