Module 5 Chem

REACTION: N₂(g) + 3H₂(g) ⇌ 2NH₃(g), ΔH = -92 kJ/mol - Heat added

Equilibrium shifts left (reverse reaction favoured and Nh3 decomposes)

REACTION: 2NO₂(g) ⇌ N₂O₄(g), ΔH = -57 kJ/mol - Volume decreased

Equilibrium shifts right (fewer gas moles on the product side)

REACTION: CO(g) + H₂O(g) ⇌ CO₂(g) + H₂(g) - H₂ removed

Equilibrium shifts right to replace H₂

REACTION: H₂(g) + I₂(g) ⇌ 2HI(g) - Initial concentrations are [H₂] = 0.5 M, [I₂] = 0.5 M, [HI] = 0 M. What happens to Q?

Q < Keq, so the reaction proceeds forward to equilibrium

REACTION: CaCO₃(s) ⇌ Ca²⁺(aq) + CO₃²⁻(aq) - Effect of adding Na₂CO₃

Equilibrium shifts left due to the common ion effect

REACTION: PbI₂(s) ⇌ Pb²⁺(aq) + 2I⁻(aq), Ksp = 7.1×10⁻⁹ - [Pb²⁺] = 1×10⁻⁴ M and [I⁻] = 1×10⁻³ M. Will a precipitate form?

Q = 1×10⁻¹⁰, so no precipitate forms (Q < Ksp)

REACTION: 2SO₂(g) + O₂(g) ⇌ 2SO₃(g), ΔH = -200 kJ/mol - Temperature decreased

Equilibrium shifts right (exothermic reaction favored)

REACTION: CH₄(g) + 2O₂(g) ⇌ CO₂(g) + 2H₂O(g) - Effect of increasing O₂ concentration

Equilibrium shifts right (forward reaction favored)

REACTION: Fe³⁺(aq) + SCN⁻(aq) ⇌ FeSCN²⁺(aq) - Color observed is pale yellow. What happens if more Fe³⁺ is added?

Equilibrium shifts right, and solution turns redder

REACTION: AgCl(s) ⇌ Ag⁺(aq) + Cl⁻(aq) - Effect of adding HCl

Equilibrium shifts left due to increased [Cl⁻] from HCl

REACTION: 2NO(g) + Cl₂(g) ⇌ 2NOCl(g), ΔH = -76 kJ/mol - Pressure increased

Equilibrium shifts right (fewer gas moles on the product side)

REACTION: 2HI(g) ⇌ H₂(g) + I₂(g), Keq = 50 at 500 K - Q is calculated as 70

Reaction shifts left (reverse reaction favored)

REACTION: BaSO₄(s) ⇌ Ba²⁺(aq) + SO₄²⁻(aq) - Solubility of BaSO₄ in water is 1.0×10⁻⁵ M. What happens if Na₂SO₄ is added?

Solubility decreases due to the common ion effect

REACTION: N₂O₄(g) ⇌ 2NO₂(g), ΔH = +58 kJ/mol - Temperature decreased

Equilibrium shifts left (exothermic reverse reaction favored)

WORD PROBLEM: CO₂(g) ⇌ CO(g) + ½O₂(g) - What happens to equilibrium if the pressure is decreased?

Equilibrium shifts right (more gas moles on the product side)

WORD PROBLEM: Pb²⁺ and I⁻ are mixed, and Q is calculated to be 5×10⁻⁸, Ksp for PbI₂ = 7×10⁻⁹ - What happens?

A precipitate forms because Q > Ksp

DELTA H = -100 - Heat added to system

Equilibrium shifts left (favoring the endothermic reverse reaction)

DELTA H = +150 - Heat removed from system

Equilibrium shifts left (favoring the exothermic reverse reaction)

VOLUME INCREASED - Effect on equilibrium

Shifts to the side with more gas moles

VOLUME DECREASED - Effect on equilibrium

Shifts to the side with fewer gas moles

PRESSURE INCREASED - Reaction has unequal gas moles

Shifts to the side with fewer gas moles

PRESSURE DECREASED - Reaction has unequal gas moles

Shifts to the side with more gas moles

CONCENTRATION INCREASE - Reactant added

Equilibrium shifts right (forward reaction favored)

CONCENTRATION DECREASE - Product removed

Equilibrium shifts right (forward reaction favored)

KEQ = 1.01 - Initial Q = 0.50

Reaction proceeds forward to reach equilibrium

KEQ = 0.021 - Initial Q = 0.50

Reaction proceeds in reverse to reach equilibrium

SOLUTION TEMPERATURE INCREASE - Endothermic reaction

Solubility increases as equilibrium shifts right

COMMON ION ADDED - Solubility of ionic compound

Decreases due to the common ion effect

KSP = 1.77×10⁻¹⁰ - Q = 2.5×10⁻⁸

No precipitate forms (Q < Ksp)

KSP = 9.8×10⁻⁹ - Precipitate observed

Q > Ksp (solubility limit exceeded)

OPEN SYSTEM - Effect on dynamic equilibrium

Equilibrium cannot be maintained reaction proceeds continuously

CLOSED SYSTEM - Effect on dynamic equilibrium

Equilibrium is maintained with constant forward and reverse reaction rates

ICE TABLE - Purpose

To calculate equilibrium concentrations and establish Keq or Q values

LE CHATELIER’S PRINCIPLE - Definition

A system at equilibrium will adjust to counteract any imposed change

HABER PROCESS - Optimal conditions

High pressure, moderate temperature, and removal of ammonia favor equilibrium yield.