Acid salt

File:Ammonium chloride.svg]]

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:{{cite book|last1=Dekock|first1=Roger L.|last2=Gray|first2=Harry B.|title=Chemical bonding and structure|date=1989|publisher=University Science Book|location=Sausalito, California|isbn=978-0-935702-61-3|pages=97–98|edition=Second|url=https://books.google.com/books?id=q77rPHP5fWMC&q=nh4cl+lewis+structure&pg=PA97|accessdate=8 February 2018}}

:{{chem2|NH3(aq) + HCl(aq) → [NH4]+Cl−(aq)}}

Acid salts are often used in foods as part of leavening agents. In this context, the acid salts are referred to as "leavening acids."{{Cite web|url=https://bakerpedia.com/ingredients/leavening-acids/|title=Leavening Acids – Baking Ingredients|last=Wallace|first=David|website=BAKERpedia|date=10 June 2015 |language=en-US|access-date=2019-10-17}} Common leavening acids include cream of tartar and monocalcium phosphate.

An acid salt can be mixed with certain base salt (such as sodium bicarbonate or baking soda) to create baking powders which release carbon dioxide.{{Cite web|url=https://www.mcgill.ca/oss/article/health-nutrition-quackery/chemistry-lesson-food-babe-and-everyone-else-12-cream-tartars-many-uses|title=The Many Uses of Cream of Tartar|website=Office for Science and Society|language=en|access-date=2019-10-17}} 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.{{Cite journal|last=Gabriala|first=Pop|s2cid=54052197|date=2007|title=RESEARCHES REGARDING THE CHEMICAL LEAVENING AGENTS' ROLE IN QUALITY OF BAKERY PRODUCTS|journal=Journal of Agroalimentary Processes and Technologies|volume=XIII, No. 1|pages=105–112}}

Disodium phosphate, {{chem2|Na2HPO4}}, is used in foods and monosodium phosphate, {{chem2|NaH2PO4}}, is used in animal feed, toothpaste and evaporated milk.

An acid with higher Acid dissociation constant value dominates the chemical reaction. It serves as a better contributor of protons ({{chem2|H(+)}}). A comparison between the {{mvar|K_a}} and Base dissociation constant indicates the acid–base property of the resulting solution by which:

1. The solution is acidic if {{math|K_a > K_b}}. It contains a greater concentration of {{chem2|H(+)}} ions than concentration of {{chem2|OH(−)}} ions due more extensive cation hydrolysis compared to that of anion hydrolysis.
2. The solution is alkaline if {{math|K_a < K_b}}. Anions hydrolyze more than cations, causing an exceeding concentration of {{chem2|OH(−)}} ions.
3. The solution is expected to be neutral only when {{math|K_a {{=}} K_b}}.{{cite book|last1=Raymond|first1=Chang|title=Chemistry|date=2010|publisher=McGraw-Hill|location=Americas, New York|isbn=978-0077274313|pages=[https://archive.org/details/Chemistry_10th_Edition_Raymond_Chang/page/n757 725]–727|edition=tenth|url=https://archive.org/details/Chemistry_10th_Edition_Raymond_Chang|accessdate=9 February 2018}}

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, {{chem2|NH4(+)}} is the main influence for acidic solution. It has greater {{mvar|K_a}} value compared to that of water molecules; {{mvar|K_a}} of {{chem2|NH4(+)}} is {{val|5.6e−10}}, and {{mvar|K_w}} of {{chem2|H2O}} is {{val|1.0e-14}}. This ensures its deprotonation when reacting with water, and is responsible for the pH below 7 at room temperature. {{chem2|Cl(-)}} will have no affinity for {{chem2|H(+)}} nor tendency to hydrolyze, as its {{mvar|K_b}} value is very low ({{mvar|K_b}} of {{chem2|Cl(-)}} is {{val|7.7e−21}}).Lower, S.K., (1999). Introduction to acid-base chemistry. Chem1 General Chemistry Text. Retrieved from http://www.chem1.com/acad/pdf/c1xacid1.pdf

Hydrolysis of ammonium at room temperature produces:

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

:$$

K_\mathrm{a} = \frac{\mathrm{[NH_3][H_3O^+]}}{\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}

• Base salt
• Salt (chemistry)
• Oxoacid
• Sodium bicarbonate
• Sodium bisulfate: an example of acid salt
• Disodium phosphate: an example of acid salt
• Monosodium phosphate: an example of acid salt

{{reflist}}

Category:Salts

Category:Acids