Chapter 3: Acids & Bases

What is a Bronsted-Lowry acid?

A substance that donates a proton (H⁺)

What is a Bronsted-Lowry base?

A substance that accepts a proton

In a Bronsted-Lowry reaction, what always moves?

A proton (H⁺) moves from the acid to the base

What is a conjugate acid?

The species formed when a base gains a proton (H⁺)

What is the conjugate base?

The species formed when an acid loses a proton (H⁺)

How can you quickly identify the acid and base in a reaction?

• Find the H⁺

• Who loses H⁺ = acid

• Who gains H⁺ = base

An example of acid and base

Label the acid, base, and the conjugates in the reaction below

b

What do curved arrows represent in reaction mechanisms?

Curved arrows show the movement of electron pairs that result in bond breaking and bond forming during a chemical reaction

base, acid

How do strong acids differ from weak acids?

Strong acids fully dissociate in solution, while weak acids partially dissociate

What does pk_a measure?

• measures acid strength

• Lower pka= stronger acid

What is the relationship between Ka and pKa?

They are inversely related:

• Large Ka → small pKa → strong acid

How much stronger is an acid with a pKa that is 1 unit lower?

It is 10x stronger

• if it goes down by 2 its acidity goes up 100X

• if it goes down by 3 it s acidity goes up 1000x

In an acid base reaction, which direction is favored?

Reactions favor formation of the weaker acid and more stable conjugate base

What is quantitative acid strength analysis?

Comparing pKa values to determine which acid or base is stronger

What is qualitative acid strength analysis?

Comparing structural stability (resonance, induction, hybridization, atom size) when pKa values are unavailable

What makes a conjugate base more stable?

• Resonance delocalization

• Higher electronegativity

• Larger atom size

• Greater s-character (sp > sp² > sp³)

How is base strength related to conjugate acid pKa?

Stronger base ↔ conjugate acid has higher pKₐ.

Name the strong acids

• HCl, HBr, HI

• H₂SO₄, HNO₃, HClO₄

The conjugate base of a strong acid is

weak

The conjugate base of a weak acid is?

strong