Chemistry XI Unit 6

Chemical equilibrium is:

when reaction stops when forward and reverse rates equal when products exceed reactants when reactants consumed

Equilibrium constant (K) is:

depends on temperature only independent of temperature depends on initial concentrations depends on catalyst

For the reaction aA + bB ⇌ cC + dD, the equilibrium expression is:

K = [A]^a + [B]^b / [C]^c + [D]^d K = [C]^c[D]^d / [A]^a[B]^b K = [A][B] / [C][D] K = (A)(B) / (C)(D)

If K >> 1:

reaction favors reactants reaction favors products reaction is at equilibrium reaction doesn't occur

If K << 1:

reaction favors reactants reaction favors products reaction at equilibrium K is negative

If K = 1:

products and reactants equal in molar amounts reaction strongly favored forward reaction strongly favored backward no equilibrium

Le Chatelier's Principle states:

system changes instantly system adjusts when disturbed system remains unchanged K changes with disturbance

When pressure increases on system at equilibrium:

shifts toward more moles gas shifts toward fewer moles gas doesn't shift K increases

When temperature increases on endothermic equilibrium:

shifts left (toward reactants) shifts right (toward products) doesn't shift K decreases

When temperature increases on exothermic equilibrium:

shifts left (toward reactants) shifts right (toward products) doesn't shift K increases

Adding catalyst to equilibrium system:

shifts equilibrium position reaches equilibrium faster increases K favors products

In Kc (concentration constant):

includes gases and solids includes only gases excludes pure liquids and solids includes all substances

In Kp (pressure constant):

uses molar concentrations uses partial pressures uses mole fractions uses volume

The relationship between Kp and Kc is:

Kp = Kc Kp = Kc(RT)^ΔN Kp = Kc/RT K = R×T

Ionic equilibrium involves:

equilibrium between ions and molecules equilibrium in solids equilibrium in gases only no equilibrium

Water ionization: H₂O ⇌ H⁺ + OH⁻, Kw =

1.0 × 10⁻14 1.0 × 10⁻7 1.0 × 10⁻12 1.0 × 10⁻2

pH is defined as:

concentration of H⁺ negative log of H⁺ concentration concentration of OH⁻ molar mass

pOH is defined as:

concentration of OH⁻ negative log of OH⁻ concentration pH + 7 hydrogen concentration

At 25°C, pH + pOH =

7 10 14 1

Basic solution has:

pH < 7 pH > 7 pH = 7 pOH = 0

Neutral solution has:

pH = 0 pH = 14 pH = 7 pOH = 7

Acid dissociation constant (Ka) measures:

strength of weak acid strength of base solubility product buffer capacity

Base dissociation constant (Kb) measures:

strength of weak base strength of acid solubility product buffer pH

The relationship Ka × Kb =

Kw K² Kc 1

Solubility product (Ksp) for AgCl is:

Ksp = [Ag⁺][Cl⁻] Ksp = [Ag⁺] + [Cl⁻] Ksp = [Ag⁺]²[Cl⁻] Ksp = [AgCl]

Buffer solution contains:

weak acid only weak base only weak acid + its conjugate base strong acid + strong base

Buffer capacity is greatest when:

[acid] >> [base] [base] >> [acid] [acid] ≈ [base] [H⁺] = 0

Henderson-Hasselbalch equation is:

pH = pKa + log([acid]/[base]) pH = pKa - log([acid]/[base]) pH = pKa + log([base]/[acid]) pH = [H⁺]

When adding small amount of acid to buffer:

pH drops significantly pH barely changes pH increases buffer breaks

When adding small amount of base to buffer:

pH rises significantly pH barely changes pH drops buffer fails

FILLBLANK:When volume decreases, pressure increases; equilibrium shifts toward _____.

fewer moles of gas

FILLBLANK:_____ decreases activation energy without changing K.

Catalyst

FILLBLANK:Kp uses _____ for gases.

partial pressures

FILLBLANK:The relationship _____ = -log[H⁺].

pH

FILLBLANK:_____ × [OH⁻] = 1.0 × 10⁻¹⁴ at 25°C.

[H⁺]

FILLBLANK:Solution with pH < 7 is _____

acidic

FILLBLANK:For conjugate pair: Ka × Kb = _____

Kw

FILLBLANK:_____ solution resists pH changes.

Buffer

FILLBLANK:Best buffer capacity when [acid] _____ [base].

equals

FILLBLANK:_____ equation: pH = pKa + log([base]/[acid]).

Henderson-Hasselbalch

FILLBLANK:Adding acid to buffer: conjugate _____ neutralizes it.

base

FILLBLANK:Adding base to buffer: weak _____ neutralizes it.

acid

TRUE/FALSE: Equilibrium means reaction stops.

TRUE FALSE

TRUE/FALSE: K depends on temperature.

TRUE FALSE

TRUE/FALSE: K is affected by catalyst.

TRUE FALSE

TRUE/FALSE: K >> 1 means products favored.

TRUE FALSE

TRUE/FALSE: K << 1 means reactants favored.

TRUE FALSE

TRUE/FALSE: Decreasing volume shifts equilibrium toward fewer moles.

TRUE FALSE

TRUE/FALSE: Adding catalyst shifts equilibrium position.

TRUE FALSE

TRUE/FALSE: pH + pOH = 14 always.

TRUE FALSE

TRUE/FALSE: pH 7 is always neutral.

TRUE FALSE

TRUE/FALSE: Larger Ka means stronger weak acid.

TRUE FALSE

TRUE/FALSE: Buffer prevents all pH change.

TRUE FALSE

TRUE/FALSE: Ksp applies to soluble salts.

TRUE FALSE