Acid-Base Chemistry Fundamentals

Acid-Base Chemistry

Definitions

• Acid: a substance that donates a proton (H+ ion)
• Base: a substance that accepts a proton (H+ ion)
• pH: a measure of acidity or basicity, ranging from 0-14
  • pH 7: neutral
  • pH < 7: acidic
  • pH > 7: basic

Acid-Base Theories

• Arrhenius Theory: acids dissociate in water to produce H+ ions, bases dissociate to produce OH- ions
• Bronsted-Lowry Theory: acids are proton donors, bases are proton acceptors
• Lewis Theory: acids are electron pair acceptors, bases are electron pair donors

pH Calculation

• pH = -log[H+]: pH is the negative logarithm of the hydrogen ion concentration
• pOH = -log[OH-]: pOH is the negative logarithm of the hydroxide ion concentration
• pH + pOH = 14: at 25°C, the sum of pH and pOH is always 14

Acid-Base Equilibrium

• K_a: acid dissociation constant, measures the strength of an acid
• K_b: base dissociation constant, measures the strength of a base
• pK_a: negative logarithm of K_a, used to compare acid strengths
• pK_b: negative logarithm of K_b, used to compare base strengths

Strong and Weak Acids/Bases

• Strong Acids: completely dissociate in water, e.g. HCl, H2SO4
• Weak Acids: partially dissociate in water, e.g. CH3COOH, HNO2
• Strong Bases: completely dissociate in water, e.g. NaOH, KOH
• Weak Bases: partially dissociate in water, e.g. NH3, CH3NH2

Acid-Base Chemistry

Definitions

• An acid is a substance that donates a proton (H+ ion).
• A base is a substance that accepts a proton (H+ ion).
• pH is a measure of acidity or basicity, ranging from 0-14, with 7 being neutral, below 7 being acidic, and above 7 being basic.

Acid-Base Theories

• Arrhenius Theory states that acids dissociate in water to produce H+ ions, while bases dissociate to produce OH- ions.
• Bronsted-Lowry Theory defines acids as proton donors and bases as proton acceptors.
• Lewis Theory describes acids as electron pair acceptors and bases as electron pair donors.

pH Calculation

• pH is calculated as the negative logarithm of the hydrogen ion concentration (pH = -log[H+]).
• pOH is calculated as the negative logarithm of the hydroxide ion concentration (pOH = -log[OH-]).
• At 25°C, the sum of pH and pOH is always 14 (pH + pOH = 14).

Acid-Base Equilibrium

• K_a is the acid dissociation constant, which measures the strength of an acid.
• K_b is the base dissociation constant, which measures the strength of a base.
• pK_a is the negative logarithm of K_a, used to compare acid strengths.
• pK_b is the negative logarithm of K_b, used to compare base strengths.

Strong and Weak Acids/Bases

• Strong acids completely dissociate in water, such as HCl and H2SO4.
• Weak acids partially dissociate in water, such as CH3COOH and HNO2.
• Strong bases completely dissociate in water, such as NaOH and KOH.
• Weak bases partially dissociate in water, such as NH3 and CH3NH2.