Chem exam 2

Buffer Solution

A solution that resists changes in pH when small amounts of acid (H⁺) or base (OH⁻) are added; it contains a weak acid and its conjugate base or a weak base and its conjugate acid.

Role of the Weak Acid in a Buffer

The weak acid reacts with added strong base (OH⁻), minimizing pH change by converting the strong base into its weaker conjugate base.

Vice Versa for Weak base reacting to strong acid

Titration Pattern (General Rule)

In a titration, before the equivalence point the solution is dominated by the initial substance, at the equivalence point it depends on the acid/base strength, and after the equivalence point the solution is dominated by the titrant added.

Titration Pattern (Weak Base + Strong Acid)

Before the equivalence point, the solution is a buffer (weak base and its conjugate acid); at equivalence, only the weak acid remains; after equivalence, excess strong acid dominates the pH.

Vice Versa

Equivalence Point pH in Titrations

At the equivalence point, pH is determined by the species remaining: strong acid + strong base gives pH = 7; weak acid + strong base gives pH > 7; weak base + strong acid gives pH < 7.

Solubility Product Constant (Ksp)

The equilibrium constant for the dissolution of a sparingly soluble ionic compound, expressed in terms of the concentrations of its aqueous ions.

Ksp value determined by?

temperature

Common Ion Effect

The solubility of a sparingly soluble salt decreases when a soluble compound containing a common ion is added, due to a shift in equilibrium that reduces dissolution.

Solubility

The mass of a salt in grams that will dissolve in 100 mL of water.

Common Ion Effect

A decrease in the solubility of an ionic compound due to the addition of a common ion.

Saturated Solution

A solution that contains the maximum amount of dissolved solute at a given temperature; any additional solute remains undissolved.

Solubility Product Constant (Ksp)

The product of the molar concentrations of dissolved ions, each raised to the power of its coefficient in the balanced equation.

Molar Solubility

The maximum number of moles of a salt that will dissolve in 1 liter of solution.

If ion product Qsp > Ksp

Precipitate

If ion product Qsp < Ksp

Dissolve

Qsp = Ksp

Equilibrium

Which compounds are ALWAYS soluble?

Group 1 metals (Li⁺, Na⁺, K⁺) and NO₃⁻ (nitrate)

Are halides (Cl⁻, Br⁻, I⁻) soluble?

Usually yes; exception: Ag⁺ (AgCl, AgBr, AgI are insoluble)

Are sulfates (SO₄²⁻) soluble?

Usually yes; some exceptions with +2/+3 metals

Are hydroxides (OH⁻) soluble?

Usually no; exceptions: Group 1, Ca²⁺, Sr²⁺, Ba²⁺

Quick rule using ion charges?

±1 ions = soluble; higher charges = more likely insoluble

What ions commonly form precipitates?

OH⁻ and other higher-charge anions

What happens if an insoluble combo forms?

A precipitate forms (solid)

Core shortcut to remember?

Group 1 + NO₃⁻ always soluble; OH⁻ usually insoluble