conjugate base

Examples of conjugate base in the following topics:

• Salts that Produce Basic Solutions

  • It is due to the fact that the anion in the salt is the conjugate base of a weak acid.
  • The bicarbonate ion is the conjugate base of carbonic acid, a weak acid.
  • Keep in mind that a salt will only be basic if it contains the conjugate base of a weak acid.
  • Sodium chloride, for instance, contains chloride (Cl-), which is the conjugate base of HCl.
  • Because the bicarbonate ion is the conjugate base of carbonic acid, a weak acid, sodium bicarbonate will yield a basic solution in water.

• Absolute Concentrations of the Acid and Conjugate Base

  • A buffer is an aqueous solution consisting of a mixture of a weak acid and its conjugate base or a weak base and its conjugate acid.
  • Therefore, it is very important to be able to identify acid and conjugate base pairs.
  • The conjugate acid is created by accepting (adding) a proton (H+) donated by the conjugate base.
  • 8.1.3 Deduce the formula of the conjugate acid/base of any Brønsted-Lowry base/acid IB Chemistry SL - YouTube
  • The conjugate base is the other product, which has had a proton removed.

• Brønsted Acids and Bases

  • The conjugate base is the ion or molecule that remains after the acid has donated its proton, and the conjugate acid is the species created after the base accepts the proton.
  • Water is amphoteric, which means it can act as either an acid or a base.
  • The acetate ion CH3CO2- is the conjugate base of acetic acid, and the hydronium ion H3O+ is the conjugate acid of the base, water:
  • The hydroxide ion is the conjugate base of water, which acts as an acid, and the ammonium ion is the conjugate acid of the base, ammonia.
  • Identify the Brønsted acid, Brønsted base, conjugate acid, and conjugate base in an acid-base reaction.

• Acidity of Amines

  • We normally think of amines as bases, but it must be remembered that 1º and 2º-amines are also very weak acids (ammonia has a pKa = 34).
  • pKa is being used as a measure of the acidity of the amine itself rather than its conjugate acid, as in the previous section.
  • The acids shown here may be converted to their conjugate bases by reaction with bases derived from weaker acids (stronger bases).
  • For complete conversion to the conjugate base, as shown, a reagent base roughly a million times stronger is required.

• Relative Amounts of Acid and Base

  • A buffer is an aqueous solution consisting of a mixture of a weak acid and its conjugate base or a weak base and its conjugate acid.
  • You can use one of these acid/conjugate base pairs:
  • Extrapolating further from this, a buffer is most effective when the concentrations of acid and conjugate base (or base and conjugate acid) are approximately equal—in other words, when the log [base]/[acid] equals 0 and the pH equals the pKa.
  • The change is minimized if the concentrations of acid and conjugate base are equal.
  • Calculate the relative amounts of a weak acid and its conjugate base that must be used to generate a buffer solution of desired pH.

• Preparing a Buffer Solution with a Specific pH

  • A buffer is a solution of weak acid and conjugate base or weak base and conjugate acid used to resist pH change with added solute.
  • A buffer is an aqueous solution containing a weak acid and its conjugate base or a weak base and its conjugate acid.
  • Buffer solutions are resistant to pH change because of the presence of an equilibrium between the acid (HA) and its conjugate base (A-).
  • If the buffer is made with a base and its conjugate acid, the pH can be adjusted using a strong acid like HCl.
  • where pH is the concentration of [H+], pKa is the acid dissociation constant, and [A-] and [HA] are concentrations of the conjugate base and starting acid.

• The Brønsted-Lowry Definition of Acids and Bases

  • Here, a conjugate base is the species that is left over after the Brønsted acid donates its proton.
  • The conjugate acid is the species that is formed when the Brønsted base accepts a proton from the Brønsted acid.
  • Therefore, according to the Brønsted-Lowry definition, an acid-base reaction is one in which a conjugate base and a conjugate acid are formed (note how this is different from the Arrhenius definition of an acid-base reaction, which is limited to the reaction of H+ with OH- to produce water).
  • The products include the acetate ion, which is the conjugate base formed in the reaction, as well as hydronium ion, which is the conjugate acid formed.
  • The conjugate acid formed in the reaction is the ammonium ion, and the conjugate base formed is hydroxide.

• Buffer Range and Capacity

  • A buffer solution usually contains a weak acid and its conjugate base.
  • When H+ is added to a buffer, the weak acid's conjugate base will accept a proton (H+), thereby "absorbing" the H+ before the pH of the solution lowers significantly.
  • Similarly, when OH- is added, the weak acid will donate a proton (H+) to its conjugate base, thereby resisting any increase in pH before shifting to a new equilibrium point.
  • Each conjugate acid-base pair has a characteristic pH range where it works as an effective buffer.
  • In other words, the pH of the equimolar solution of acid (e.g., when the ratio of the concentration of acid and conjugate base is 1:1) is equal to the pKa.

• Buffers Containing a Base and Conjugate Acid

  • An alkaline buffer can be made from a mixture of the base and its conjugate acid, but the formulas for determining pH take a different form.
  • An alkaline buffer can be made from a mixture of a base and its conjugate acid, similar to the way in which weak acids and their conjugate bases can be used to make a buffer.
  • By multiplying a conjugate acid (such as NH4+) and a conjugate base (such as NH3) the following is given:
  • Two-dimensional image depicting the association of proton (H+) with the weak base ammonia (NH3) to form its conjugate acid, ammonium ion (NH4+).
  • Calculate the pH of an alkaline buffer system consisting of a weak base and its conjugate acid.

• Strong Bases

  • When writing out the dissociation equation of a strong base, assume that the reverse reaction does not occur, because the conjugate acid of a strong base is very weak.
  • Group 1 salts of carbanions (such as butyllithium, LiC4H9, which dissociates into Li+ and the carbanion C4H9-), amides (NH2-), and hydrides (H-) tend to be even stronger bases due to the extreme weakness of their conjugate acids—stable hydrocarbons, amines, and hydrogen gas.
  • Usually, these bases are created by adding pure alkali metals in their neutral state, such as sodium, to the conjugate acid.
  • For example, the ethoxide ion (conjugate base of ethanol) will undergo this reaction in the presence of water:
  • Unlike weak bases, which exist in equilibrium with their conjugate acids, the strong base reacts completely with water, and none of the original anion remains after the base is added to solution.