Definition Of Strength Of Acids And Bases
Strong electrolytes are completely dissociated into ions in water. The acid or base molecule does not exist in aqueous solution, only ions. Weak electrolytes are incompletely dissociated.
More About Strength of acids and bases
- Strong acids completely dissociate in water, forming H+ and an anion
- There are six strong acids. The others are considered to be weak acids
- HCl - hydrochloric acid, HNO3- nitric acid, H2 SO4 - sulfuric acid
- HBr - hydrobromic acid, HI - hydroiodic acid and, HClO4 - perchloric acid
- 100% dissociation isn't true as solutions become more concentrated. If the acid is 100% dissociated in solutions of 1.0 M or less, it is called strong. Sulfuric acid is considered strong only in its first dissociation step.
- H2SO4 → HSO4- + H +
- A weak acid only partially dissociates in water to give and the anion. Examples of weak acids include hydrofluoric acid, HF, and acetic acid,
- Weak acids include:
- Molecules that contain an ionizable proton. A molecule with a formula starting with H usually is an acid
- Organic acids containing one or more carboxyl group, -COOH. The H is ionizable
- Anions with an ionizable proton. (e.g,HSO4- → SO4 + H+ )
- Cations: transition metal cations, heavy metal cations with high charge
- NH4+ Dissociates into NH3 +
- Strong bases dissociate 100% into the cation and OH+ (hydroxide ion). The hydroxides of the Group I and Group II metals usually are considered to be strong bases
- Examples of weak bases include ammonia, NH3 + H+ , and diethyl amine,
- Most weak bases are anions of weak acids.
- Weak bases do not furnish OH- ions by dissociation. Instead, they react with water to generate OH- ions.
- Acids and bases exist as conjugate acid-base pairs. The term conjugate comes from the Latin stems meaning "joined together" and refers to things that are joined, particularly in pairs, such as Bronsted acids and bases
- pH predicts the strength of acids and bases
- the value of pH ranges between 0 – 14
- The strength of various acids and bases is expressed on the pH scale. The pH scale is a 14 point scale, which expresses the strength of an acid or a base in terms of the hydronium ion ( ) concentration
- The range from 0 to 14 gives a measurement of comparative strength of acid and base solutions
- The strength of acids and bases can be expressed in terms of the concentration of hydrogen ions, i.e., hydronium ions (H3O+) or hydroxyl ions in a solution
- Pure water and other neutral solutions have a pH value of 7. A pH value less than 7 indicates that the solution is acidic, and a pH value greater than 7 indicates that the solution is basic