Acid base equilibrium

What is an Arrhenius acid?

A substance that donates H⁺ ions in aqueous solution.

What is an Arrhenius base?

A substance that donates OH⁻ ions in aqueous solution.

What is a Brønsted‑Lowry acid?

A substance that donates a proton (H⁺).

What is a Brønsted‑Lowry base?

A substance that accepts a proton (H⁺).

What is a Lewis acid?

An electron pair acceptor.

What is a Lewis base?

An electron pair donor.

Which acid/base definition is the broadest?

Lewis acid-base theory.

What is the conjugate base of an acid?

The product formed when the acid loses an H⁺.

What is the conjugate acid of a base?

The product formed when the base gains an H⁺.

How do you draw a conjugate base?

Remove one H⁺ and decrease the charge by 1.

How do you draw a conjugate acid?

Add one H⁺ and increase the charge by 1.

What does "amphiprotic" mean?

A substance that can both donate and accept H⁺.

What does "amphoteric" mean?

A substance that can act as both an acid and a base.

Is water amphiprotic, amphoteric, or both?

Both.

What is the autoionization of water equation?

2 H₂O ⇌ H₃O⁺ + OH⁻

What is KW at 25 °C?

Kw = [H₃O⁺][OH⁻] = 1.0 × 10⁻¹⁴

What are the 7 strong acids?

HCl, HBr, HI, HNO₃, HClO₃, HClO₄, H₂SO₄ ✨Mnemonic: "So I Brought No Clean Clothes, Please Hurry"

Which strong acids are binary?

HCl, HBr, HI ✨Mnemonic (part of full): "Clean Clothes" = Cl, Br, I

Which strong acids are oxyacids?

HNO₃, HClO₃, HClO₄, H₂SO₄ ✨Mnemonic (part of full): "No Clean Clothes, Please Hurry"

What is the trend for binary acid strength across a row?

Increases → due to increasing electronegativity

What is the trend for binary acid strength down a column?

Increases ↓ due to increasing atomic size

Order the halogen binary acids from strongest to weakest.

HI > HBr > HCl > HF

Why is HF a weak acid?

Because the bond is too strong and hard to break

Which is stronger: HCl or HBr?

HBr (because iodine is larger and bond is weaker)

What is the trend for oxyacid strength with oxygen atoms?

More O atoms = stronger acid

Why does more oxygen make an oxyacid stronger?

More resonance → more stable conjugate base → stronger acid

What is the trend for oxyacid strength with heteroatom electronegativity?

More electronegative heteroatom = stronger acid

Which is stronger: HClO₄ or HBrO₄?

HClO₄ (Cl is more electronegative)

Does size matter in oxyacid strength?

No—electronegativity and oxygen count are what matter

What stabilizes a conjugate base in oxyacids?

Resonance and inductive effects

What causes the inductive effect in oxyacids?

Electronegative atoms pulling electron density

What is a neutralization reaction?

A reaction between an acid and a base that produces water and a salt.

Write the general formula of a neutralization reaction.

Acid + Base → H₂O + Salt

What type of reaction is a neutralization reaction also called?

A metathesis (double-displacement) reaction.

What is the pH of a neutralization between a strong acid and strong base?

pH = 7.0 (neutral)

What is the pH of a neutralization between a weak acid and strong base?

pH > 7.0 (basic)

What is the pH of a neutralization between a weak base and strong acid?

pH < 7.0 (acidic)

What is the neutralization calculation equation?

nA·MAVA = nB·MBVB

What does MA stand for in the neutralization equation?

Molarity of the acid.

What does VA stand for in the neutralization equation?

Volume of the acid.

What does MB stand for in the neutralization equation?

Molarity of the base.

What does VB stand for in the neutralization equation?

Volume of the base.

What does nA represent?

Number of H⁺ ions the acid can donate.

What does nB represent?

Number of OH⁻ ions the base can donate.

How is molarity (M) defined?

Moles of solute per liter of solution.

How is normality (N) defined?

Moles of reactive species (H⁺ or OH⁻) per liter of solution.

Why is normality more accurate than molarity in acid-base reactions?

Because normality accounts for the number of available protons or hydroxide ions, not just moles of compound.

How many H⁺ ions can phosphoric acid (H₃PO₄) donate?

Three H⁺ ions.

What is the value of nA for H₃PO₄ in neutralization calculations?

nA = 3

What is produced in a neutralization reaction?

Water and a salt.

How is a salt defined in terms of neutralization reactions?

The ionic product of a neutralization reaction.

What does hydrolysis of salts refer to?

Dissolving salts in water and their effect on water's pH.

Name neutral cations that do not affect pH when dissolved.

Group 1 and Group 2 metals.

Name neutral anions that do not affect pH when dissolved.

Cl⁻, Br⁻, I⁻, NO₃⁻, ClO₄⁻, ClO₃⁻.

How do most cations behave in water?

They act as acids (often Lewis acids).

How do most anions behave in water?

They act as bases (often Lewis bases).

Which anion is an exception and acts as an acid?

HSO₄⁻.

Is NH₄I acidic, basic, or neutral when dissolved?

Acidic.

Is NaNO₃ acidic, basic, or neutral when dissolved?

Neutral.

Is KF acidic, basic, or neutral when dissolved?

Basic.

Are ZnCl₂ and Al(NO₃)₃ acidic, basic, or neutral when dissolved?

Acidic.

How does adding acid affect solubility of salts with basic anions?

It increases solubility by reacting with basic anions.

What happens to KF solubility when acid is added?

It increases because F⁻ reacts with added H⁺ to form HF.

How does increasing pH affect solubility of salts with acidic cations?

It increases solubility by reacting with acidic cations.

What could increase the solubility of CaF₂?

Adding acid (HCl) to lower pH.

Which substances would increase CaF₂ solubility?

HCl (acidic substance).

Which substances would increase NH₄Cl solubility?

Ca(OH)₂ (basic substance).

Why do basic salts increase solubility upon adding acid?

Because acid neutralizes the basic anion, shifting equilibrium.

Why do acidic salts increase solubility upon adding base?

Because base neutralizes the acidic cation, shifting equilibrium.

What is titration?

A method used to determine the concentration of an unknown solution by reacting it with a known solution.

What is the titrant?

The solution of known concentration added from a burette.

What is the titrand?

The unknown solution in the Erlenmeyer flask being analyzed.

What is a titration curve?

A graph showing pH change as titrant is added to the titrand.

What is the equivalence point?

The point where moles of acid equal moles of base.

Strong acid + strong base equivalence point

pH = 7

Weak acid + strong base equivalence point

pH > 7 (due to conjugate base)

Weak base + strong acid equivalence point

pH < 7 (due to conjugate acid)

Why does a weak acid + strong base have pH > 7 at equivalence?

Because the conjugate base formed is basic and increases the pH.

Why does a weak base + strong acid have pH < 7 at equivalence?

Because the conjugate acid formed is acidic and lowers the pH.

What is the half-equivalence point?

The point where [HA] = [A⁻]; pH = pKa

What does the inflection point on a titration curve represent?

The equivalence point

What happens at the half-equivalence point?

Exactly half of the weak acid is neutralized; pH = pKa

What is a polyprotic acid?

An acid that donates more than one proton (e.g. H₂SO₄)

How does H₂SO₄ dissociate?

H₂SO₄ → H⁺ + HSO₄⁻ → H⁺ + SO₄²⁻

How many pKa values does a polyprotic acid have?

One for each proton it donates (e.g., H₂SO₄ has pKa₁ and pKa₂)

What does pKa₁ represent?

The pH where [H₂A] = [HA⁻]

What does pKa₂ represent?

The pH where [HA⁻] = [A²⁻]

At pH < pKa₁

Mostly H₂A (fully protonated form) is present

At pKa₁ < pH < pKa₂

Mostly HA⁻ (intermediate form) is present

At pH > pKa₂

Mostly A²⁻ (fully deprotonated form) is present

Titration curve of strong acid with strong base

Sharp increase, equivalence point at pH 7

Titration curve of weak acid with strong base

Starts higher, slow increase then steep, equivalence point pH > 7

Titration curve of weak base with strong acid

Starts basic, gradual decrease then sharp drop, equivalence point pH < 7