Fast and reliable theoretical determination of pKa* for photoacids

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Acid and Bases: Ka, pKa, and Relative Strengths02:35

Acid and Bases: Ka, pKa, and Relative Strengths

This lesson delves into a critical aspect of the relative strengths of acids and bases. The strength of an acid is evaluated by the acid dissociation into its conjugate base and a hydronium ion in water. The complete dissociation of a strong acid is confirmed with a very high concentration of hydronium ions. As a result, an incomplete dissociation process affirms a weak acid. Therefore, the equilibrium is in the forward direction for strong acids and backward for weak acids in these reactions.
Polyprotic Acids03:38

Polyprotic Acids

Acids are classified by the number of protons per molecule that they can give up in a reaction. Acids such as HCl, HNO3, and HCN that contain one ionizable hydrogen atom in each molecule are called monoprotic acids. Their reactions with water are:
Titration of a Weak Acid with a Strong Base01:30

Titration of a Weak Acid with a Strong Base

In titrating a weak acid with a strong base, different calculation methods are applied at various stages. Initially, the pH of a weak acid like acetic acid is calculated using its dissociation constant (Ka) and an ICE table. Upon addition of a strong base such as sodium hydroxide, a buffer forms, and its pH is determined using the Henderson-Hasselbalch equation. As more base is added and the titration reaches the halfway point, the pH becomes equal to the pKa of the acid, indicating equal...
Titration of a Polyprotic Acid02:08

Titration of a Polyprotic Acid

A polyprotic acid contains more than one ionizable hydrogen and undergoes a stepwise ionization process. If the acid dissociation constants of the ionizable protons differ sufficiently from each other, then the titration curve for such polyprotic acid generates a distinct equivalence point for each of its ionizable hydrogens. Therefore, titration of a diprotic acid results in the formation of two equivalence points, whereas the titration of a triprotic acid results in the formation of three...
Acidity of Carboxylic Acids01:21

Acidity of Carboxylic Acids

Carboxylic acids are the strongest organic acids. However, their acidic strength is much less than mineral acids like HCl. Carboxylic acids ionize in water and readily lose the hydroxyl proton to form a resonance-stabilized carboxylate ion.
Relative Strengths of Conjugate Acid-Base Pairs02:29

Relative Strengths of Conjugate Acid-Base Pairs

Brønsted-Lowry acid-base chemistry is the transfer of protons; thus, logic suggests a relation between the relative strengths of conjugate acid-base pairs. The strength of an acid or base is quantified in its ionization constant, Ka or Kb, which represents the extent of the acid or base ionization reaction. For the conjugate acid-base pair HA / A−, the ionization equilibrium equations and ionization constant expressions are