Chapter 13: SolutionsChapter 13: Solutions

13.1 Types of Solutions

Mixture• A blend of 2 or more kinds

of matter, each of which retain its own identity & properties.

Solution• Solutions: homogeneous

mixtures of 2 or more substances in a single phase.

Components of Solutions

• Solute – the substance being dissolved (the lemonade mix)

• Solvent – the substance doing the dissolving (the water)

• Soluble – when a substance is able to be dissolved into another substance (lemonade mix into water)

• Insoluble – when a substance is unable to be dissolved into another substance (oil and water)

Types of Solutions1. Solid Solutions- most

common are ALLOYS (a mix of 2 or more metals)

2. Gaseous Solutions – all mixtures of gases are solutions because they can all diffuse through each other. Ex: air

3. Liquid Solutions - both solvent and solute are liquids. We use the terms miscible and immiscible

4. Aqueous Solutions – when water is the solvent in the soln.

Suspensions & Colloids• Suspension: the particles in a solvent are so large that they

settle out unless the mixture is constantly stirred/agitated.

• Colloid: particles that are in between the size in solutions and suspensions. (colloidal dispersions)

Tyndall Effect

• Tyndall Effect- Light is dispersed by a colloidal particles in a transparent medium.

Solutes: Electrolytes vs. Nonelectrolytes

• Substances which dissolve in H2O are classified by what they make: Ions or molecules.

• Electrolytes: form ions in water and conducts currents. http://www.flixya.com/video/498469/How_To_Charge_An_IPod_Using_Electrolytes_And_An_On

• Nonelectrolytes: form molecules in water and does NOT conduct electricity.

13.2 The Solution Process• The rate at which a solid solute dissolves in a

solutions depends on 3 factors:– Surface area - increase SA, increase rate of

dissolving. (what dissolves faster, a block of NaCl or small flakes of NaCl?)

– Stirring – by stirring, you sweep away already dissolved parts and expose new SA.

– Temperature – higher the temperature the more kinetic energy, the faster the particles are moving, the faster the solid will dissolve.

Solubility

• Solution Equilibrium- when dissolution and crystallization of a solution occur at the same time.

Saturated vs. Unsaturated Soln.s

• Saturated Soln- a soln that contains the maximum amount of dissolved soulute.

• Unsaturated soln- a soln that contains less solute than a saturated soln contains.

Supersaturation!• Supersaturated soln- a solution that contains

MORE dissolved solute than a saturated solution under the same conditions.

• As the soln cools, the extra solute remains in soln and creates the supersaturated state.

• To encourage crystallization, uses a “seed” crystal.

• http://www.youtube.com/watch?v=7iNG1tTVeyA

• Solubility values- the amount of substance required to forms a saturated soln with a specific amount of solvent at a specified temp.

Solute-Solvent Interactions

• “Like dissolves like” is the key to understanding theses interactions. Translation: polar compounds interact with other polar compounds, & non-polar with non-polar.

• Dissolving ionic compound in aqueous solns- is called hydration. H2O is polar and will interact with ionic compounds.

• Ionics do not dissolve in non-polar solns.

Effects of pressure on Solubility

• Pressure does not effect solubility rates of solid and liquid solns. However, it does effect Gas solns.

• Increasing the pressure increases the solubility, and increases vaporization as per Le Châtelier’s principle.

Henry’s Law

• “The solubility of a gas in a liquid is directly proportional to the partial pressure of that gas on the surface of the liquid.”

• Effervescence- the rapid escape of a gas from the liquid solvent.

Heats of Solution

• “The formation of a solution is accompanied by an energy change.”

• Exothermic- when there is a net loss (or release) of energy/heat in the system

• Endothermic- when there is a net gain (or absorption) of energy/heat to the system.

• Heat of Solution – the net amount of energy absorbed or released when a specific amount of solute dissolves is a solvent.

13.3 Concentrations of Solutions

• Concentration- the measure of the amount of solute in a given amount of solvent or soln.

• Dilute: “small” amount of solute in solvent.• Concentrated: “large” amount of solute in

solvent.

Molarity

– Molarity- # of moles of solute in ONE liter of solvent. Units: (mol/L)

• Formula: Molarity = Moles of solute ÷ liters of soln.

Ex: What is the molarity of a soln. of 0.1019 mols of H2SO4 with enough water to make 0.100 L of soln.?

Molality

• Molality- concentration of a soln expressed in moles of solute per kilogram of solvent.

Molality = moles of solute ÷ Kg of solvent

Ex: Chlorine is often added to water in swimming pools and to drinking water to keep the water free and clear of living organisms. What is the molality of 0.227 mols of Cl2 and 5000g H2O?