MCAT Chemistry

Acids & Bases

MCAT Chemistry > Acids & Bases

Background

There are many different definitions on what exactly bases and acids do, however the MCAT will test all of them so understanding how these important molecules react is essential in being successful come test day. Not only in chemistry, but acids and bases play key roles in the human body systems and understanding these concepts is essential in becoming a successful doctor.

Classification Systems

Arrhanius System

Arrhanius System

Bronsted-Lowry System

Bronsted-Lowry System contains the concept of conjugate base pairs

Lewis System

Lewis System

Nomenclature

The nomenclature is related to parent anion name.

Acids end with the suffix –ide or by adding the prefix hydro- and ending with the suffix –ic

Oxyoacids are acids formed from oxyanions.

If the anion ends in –ite (less O), acid will be –ous acid, if the anion ends in –ate (more O), than the acid will end with –ic acid

Hypo = inadequate, Hyper = excessive

Water Auto-Ionization

See Water Auto-Ionization

Water Auto-Ionization is a property that allows water act as an amphoteric species, which is a substance that in the presence of a base reacts like an acid, and in the presence of an acid, acts like a base.

pH and pOH

See pH and pOH

Strong Acids and Bases

Strong Acids and Bases completely dissociate into constituent ions in aqueous solutions

NaOH + H2O → Na+ + OH-

Strong Acids

See Strong Acids

Strong Bases

See Strong Bases

Weak Acids and Bases

Weak Acids and Bases are weak to the degree that which they partially dissociate.

The smaller the value of Ka, the weaker the acid and the less dissociation

HA + H2O ←→ H3O+ + A-

Ka = [H30+]([A-]/[HA])

The pH of a solution containing a weak acid/weak base depends on the strength of the reactants. When a weak acid reacts with a strong base, the pH of the solution at equilibrium is basic because salt hydrolyzes to reform acid and with concurrent formation of the OH- ions from H2O, the reaction will shift away from autoionization, [H+/H3O+] decreases, [OH-] greater than [H+].

CH3COOH + NaOH ←→ Na+ + CH3COO- + H2O

CH3COO- + H2O ←→ CH3COOH + OH-

Weak Acids

See Weak Acids

Weak Bases

See Weak Bases

Conjugate Base Pairs

See Conjugate Base Pairs

Titrations

See Titrations

Buffers

See Buffers

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Acids & Bases

Acids & Bases Topics

MCAT Chemistry

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