Chemistry Comprehensive: Solutions, Solubility, and Colligative Properties

What is a solution?

A homogeneous mixture of solute and solvent.

What is a solute?

A substance being dissolved, like salt.

What is a solvent?

A substance doing the dissolving, like water.

What is a homogeneous mixture?

A mixture that is uniform throughout and looks the same everywhere.

What is a heterogeneous mixture?

A mixture that is not uniform; different parts or phases can be seen.

What is an electrolyte?

A substance that conducts electricity when dissolved in water.

What is a strong electrolyte?

A substance that dissociates 100% into ions, such as ionic compounds and strong acids.

What is a weak electrolyte?

A substance that partially dissociates into ions, such as weak acids.

What is a non-electrolyte?

A substance that does not dissociate into ions and does not conduct electricity, like sugar or ethanol.

What is dissociation?

The process of ionic compounds breaking into individual ions in water.

What is solvation?

The process where solvent particles surround and pull apart solute particles.

What is hydration?

Solvation when water is the solvent.

What is the heat of solution?

The total energy change when a solute dissolves in a solvent.

What are the three factors that speed up dissolving?

1. Agitation (stirring), 2. More surface area (crushing), 3. Higher temperature.

What is an unsaturated solution?

A solution that can still dissolve more solute.

What is a saturated solution?

A solution that has dissolved the maximum amount possible and cannot dissolve more.

What is a supersaturated solution?

A solution that contains more than the maximum amount of solute; it is unstable and will crystallize if disturbed.

What does the 'like dissolves like' rule state?

Polar substances dissolve polar substances, and nonpolar substances dissolve nonpolar substances.

How does temperature affect the solubility of solids?

Most solids become more soluble as temperature increases.

How does temperature affect the solubility of gases?

Gases become less soluble as temperature increases.

How does pressure affect the solubility of gases?

Gases become more soluble as pressure increases (Henry's Law).

How do you read a solubility curve?

On the line = saturated, below the line = unsaturated, above the line = supersaturated.

Which substance decreases in solubility as temperature increases?

Gases, such as NH₃ and CO₂.

What is the definition of molarity?

Concentration measured as moles of solute per liter of solution.

What is the formula for molarity?

M = moles of solute ÷ liters of solution.

What is an important step in calculating molarity?

Always convert mL to L first (mL ÷ 1000 = L).

What is dilution?

Adding more solvent to make a solution less concentrated.

What is the dilution formula?

M₁V₁ = M₂V₂ (moles before dilution = moles after).

What is the definition of molality?

Moles of solute per kilogram of solvent.

What is the formula for molality?

m = moles of solute ÷ kilograms of solvent.

What is the difference between molarity and molality?

Molarity uses liters of solution; molality uses kilograms of solvent.

What are colligative properties?

Properties that depend on the number of solute particles, not their identity.

What are the four colligative properties?

1. Vapor pressure lowering, 2. Boiling point elevation, 3. Freezing point depression, 4. Osmotic pressure.

What is the Van't Hoff factor (i)?

The number of particles a formula unit produces when dissolved.

Give examples of Van't Hoff factors.

NaCl → i=2 (Na⁺ + Cl⁻), CaCl₂ → i=3 (Ca²⁺ + 2Cl⁻), Glucose → i=1 (doesn't break apart).

What is the boiling point elevation formula?

ΔTb = i × Kb × m.

What is water's boiling point constant (K_b)?

K_b = 100°C or what is given

What is the new boiling point formula?

New BP = 100°C + ΔT_b.

What is the freezing point depression formula?

ΔTf = i × Kf × m.

What is water's freezing point constant (K_f)?

K_f = 1.86 °C/m.

What is the new freezing point formula?

FP = 0°C - ΔT_f.

Why does salt melt ice?

Salt lowers the freezing point of water below 0°C.

Why does antifreeze work?

It lowers the freezing point and raises the boiling point of water in a car.

Why does soda fizz when opened?

Pressure drops, causing gas to become less soluble and bubbles to form.

What is the common mix-up between their formulas molarity and molality?

Molarity = mol/L of solution;

Molality = mol/kg of solvent.

What is the common mix-up regarding gas vs. solid solubility with heat?

Solids are more soluble when hot; gases are less soluble when hot.

What is the difference between saturated and unsaturated solutions?

Saturated = full, can't dissolve more; unsaturated = can dissolve more.

What is the difference between electrolytes and non-electrolytes?

Electrolytes conduct electricity (ionic); non-electrolytes don't (covalent).

What does a solubility curve show?

How much solute can dissolve at different temperatures.

Which substance on solubility curves is most affected by temperature?

The one with the steepest slope, usually KNO₃.

Which substance on solubility curves is least affected by temperature?

The one with the flattest slope, usually NaCl.