Medical Chemistry Lecture Notes Lecture 8 Salts PDF

Medical chemistry Department of dentistry st 1 stage Lecturer: Dr.Mazin Hasan Lec8: Salts Dr. Mazin Hasan Medical chemistry Salts: Salt is defined as the substance that is derived from acid and base. And since there are strong acids...

Medical chemistry Department of dentistry st 1 stage Lecturer: Dr.Mazin Hasan Lec8: Salts Dr. Mazin Hasan Medical chemistry Salts: Salt is defined as the substance that is derived from acid and base. And since there are strong acids and bases, as well as weak acids and bases, the process of forming salt will depend on the type of acid and the base reacting to its production, and for this the salts have four types according to their derivation, namely: 1. Salts derived from strong acids and strong bases, such as NaCl, which is produced from the reaction of hydrochloric acid (HCl) with sodium hydroxide (NaOH) according to the following formula: 2. Salts derived from strong acids and weak bases, such as (NH4Cl), which is produced from the reaction of hydrochloric acid (HCl) with ammonium hydroxide (NH4OH) according to the following formula: 3.Salts derived from weak acids and strong bases, such as(CH3COONa ), which is produced from the reaction of acetic acid (CH3COOH) with sodium hydroxide (NaOH) according to the following formula: 4.Salts derived from weak acids and weak bases, such as(CH3COONH4 ), which is produced from the reaction of acetic acid (CH3COOH) with ammonium hydroxide (NaOH) according to the following formula: Ionization of salts: The solutions of salts formed from the reaction of equal quantities of acid and base appear to be neutral, but many of them are not so they may be acidic and may be alkaline and this of course is a result of the strength of the acid or the base from which that salt is derived, and as mentioned earlier there are four types of salts according to their derivation from Acids and bases. The following ionize these four types: 1. Ionization of salts derived from strong acid and strong base: The hydrolysis of a salt is the reaction of one or both salts with water. For example, sodium chloride is ionized according to the following formula: This type of salts does not affect the pH because the products, which are sodium hydroxide and hydrochloric acid, are strong electrolytes, i.e. they will ionize completely, and chloride ions [Cl-] and sodium ions [Na +] are acids and bases corresponding to the bases and acids conjugate, so the sodium ion does not tend to react with the hydroxide resulting from the dissociation of water, the chloride ion does not tend to react with the hydrogen ion resulting from the dissolution of the water, and thus has no effect on equilibrium and the solutions of this product of salts have a neutral effect, pH= 7 2. Ionization of salts derived from strong acid and weak base: The solutions of these salts give an apparent increase in the concentration of hydrogen ions because the hydroxide ions will interact with the positive ions of the weak base forming a weak base with little dissociation, (pH 7 assuming that we have salt (NaA) will ionized in water according to the following formula: The anion (A-) will react with hydroxide ion and formation weak acid: 4. Ionization of salts derived from weak acid and strong base: We have compare between strengths the acid and base which produced this the salt from during values the ionization constants Ka and Kb. If Ka = Kb ( is neutral salt) If Ka > Kb ( is acidic salt) If Kb > Ka ( is alkaline salt) Salts derived from a weak acid and a weak base such as ammonium acetate are ionized according to the following equation: