Experience 3: Reactions in Aqueous Solutions

What is Coulomb's Law, and how does it relate to ionic compounds?

Coulomb's Law (F = kQ₁Q₂/r²) describes the force of attraction between ions. Stronger charges/shorter distances make ionic bonds harder to break, reducing solubility.

What is a solvation shell?

A sphere of solvent molecules (e.g., water) that surrounds and separates dissolved ions, enabling solubility.

What is the key difference between a complete ionic equation and a net ionic equation?

The complete ionic equation shows all dissolved ions, while the net ionic equation omits spectator ions to focus only on reacting species.

Identify the spectator ions in: Ag⁺(aq) + NO₃⁻(aq) + Na⁺(aq) + Cl⁻(aq) → AgCl(s) + Na⁺(aq) + NO₃⁻(aq)

Na⁺ and NO₃⁻ (they appear unchanged on both sides).

Write the net ionic equation for: FeCl₃(aq) + 3KOH(aq) → Fe(OH)₃(s) + 3KCl(aq)

Fe³⁺(aq) + 3OH⁻(aq) → Fe(OH)₃(s).

List the steps to write a net ionic equation.

1. Write the balanced molecular equation. 2. Split strong electrolytes into ions (complete ionic equation). 3. Cancel spectator ions. 4. Write the remaining species (net ionic equation).

Are all nitrate (NO₃⁻) salts soluble?

Yes, with very few exceptions.

Which sulfate (SO₄²⁻) salts are insoluble?

PbSO₄, Ag₂SO₄, BaSO₄, SrSO₄, Hg₂SO₄, and CaSO₄.

Why is AgCl insoluble in water?

The strong attraction between Ag⁺ and Cl⁻ ions resists dissociation by water molecules.

Which ion groups are always soluble (no exceptions)?

Group 1A cations (Na⁺, K⁺, etc.) and ammonium (NH₄⁺) salts.

How does adding KCl affect the solubility of PbCl₂?

It decreases solubility due to the common-ion effect (Cl⁻ shifts equilibrium toward solid PbCl₂).

According to Le Chatelier's Principle, what happens if heat is added to an endothermic dissolution reaction?

More products (dissolved ions) form to absorb the added heat.

What happens to solubility equilibrium if the concentration of Cl⁻ is increased in AgCl ⇌ Ag⁺ + Cl⁻?

Equilibrium shifts left (toward solid AgCl) to reduce the stress of excess Cl⁻.

Predict the precipitate (if any) when Na₂SO₄(aq) and BaCl₂(aq) are mixed. Write the net ionic equation.

Precipitate: BaSO₄(s). Net ionic: Ba²⁺(aq) + SO₄²⁻(aq) → BaSO₄(s).

What is the common-ion effect?

The decrease in solubility of an ionic compound when a soluble compound with a shared ion is added to the solution (due to Le Chatelier's Principle).

What holds ionic solids together?

The electrostatic force of attraction between positively and negatively charged ions (Coulombic attraction).

What happens to ionic compounds when they interact with water?

Polar water molecules attract and surround the ions, causing them to dissolve (if the water-ion attraction overcomes the ionic bond strength).

What is a precipitation reaction?

A reaction where two soluble ionic compounds react to form an insoluble solid (precipitate) and a soluble compound.

What is the general form of a double-displacement reaction?

AB + CD → AD + CB.

What is the solubility product constant (Ksp)?

The equilibrium constant for the dissolution of a sparingly soluble ionic compound.

How does temperature affect the solubility of most solids?

Increasing temperature generally increases solubility (for endothermic dissolution processes).

What is the difference between Qsp and Ksp?

Qsp is the reaction quotient (current ion product), while Ksp is the equilibrium constant. If Qsp > Ksp, precipitation occurs.

What is Le Chatelier's Principle?

When a system at equilibrium is disturbed, it will shift to counteract the change and restore equilibrium.

How does the common-ion effect relate to Le Chatelier's Principle?

Adding a common ion disturbs equilibrium, causing the system to shift toward the solid to reduce the ion concentration.

Are chloride (Cl⁻) salts generally soluble?

Yes, except when paired with Ag⁺, Hg₂²⁺, or Pb²⁺.

What happens to the solubility of AgCl if NaCl is added to the solution?

Solubility decreases due to the common Cl⁻ ion (common-ion effect).

Write the net ionic equation for: CuCl₂(aq) + K₃PO₄(aq) → KCl(aq) + Cu₃(PO₄)₂(s)

3Cu²⁺(aq) + 2PO₄³⁻(aq) → Cu₃(PO₄)₂(s).

What are the solubility rules for hydroxide (OH⁻) compounds?

Most are insoluble, except when paired with Group 1A cations or NH₄⁺.

Why do some ionic compounds dissolve easily while others don't?

It depends on the strength of ionic bonds (determined by charge and size) versus the attraction between ions and water molecules.

How can you predict if a precipitate will form in a reaction?

Use solubility rules to check if any product is insoluble, or compare Qsp to Ksp.