Mixtures and Solutions

Types of Mixtures

• Heterogeneous –

• Homogeneous

Heterogeneous mixtures

• Suspensions –

– Particle size:

• Colloids –

– Particle size:

– Brownian motion:

– Tyndall effect:

Homogeneous Mixtures

• Solutions

– Solute

– Solvent

– Can be solid, liquid, or gas

• Soluble -

• Insoluble -

• Miscible -

• Immiscible -

Solution Concentration

• Measure of how much solute is dissolved in a specific amount of solvent or solution– Qualitative: Concentrated vs. Dilute– Quantitative: % by mass, % by volume, Molarity

• % by mass:

• In order to maintain a sodium chloride concentration similar to ocean water, an aquarium must contain 3.6 g NaCl per 100.0 g of water. What is the percent by mass of the NaCl in the solution?

• You have 1500.0 g of a bleach solution. The percent by mass of the solute (NaOCl) is 3.62%. How many grams of NaOCl are in the solution?

• % by volume – used when both solute and solvent are liquid

• What is the percent by volume of ethanol in a solution that contains 35mL of ethanol dissolved in 155 mL of water?

• What is the percent by volume of isopropyl alcohol in a solution that contains 24 mL of isopropyl alcohol in 1.1 L of water?

• Molarity (M)

• What is the molarity of a solution containing 3 moles of solute in 1.5 L of solution?

• What is the molarity of 155 mL of solution containing 1.55 g dissolved KBr?

• Preparing molar solutions

• How many grams of CaCl2 would be dissolved in 1.0 L of a 0.10 M solution of CaCl2?

• What mass of NaOH is in 250 mL of a 3.0 M NaOH solution?

• Diluting molar solutions:

• What volume of 2.00M CaCl2 stock solution would you use to make 0.50L of 0.300M CaCl2 solution?

• How many mL of 5.0 M H2SO4 stock solution would you need to prepare 100.0 mL of 0.25M H2SO4?

Factors Affecting Solvation

• Temperature• Pressure• Polarity

Solvation Process

• To form a solution solute particles must separate and the solute and solvent particles must mix

• Solvent particles surround surface of the solid solute– Forces between solute and solvent > forces

holding solute together

• Solvation -

Ways to increase solvation

• Increase collisions between solute and solvent particles

• Agitation• Increase surface area• Increase temperature

Solubility

• Unsaturated solutions

• Saturated solutions

• Supersaturated solutions

• Solubility of gases – less soluble at higher temperatures

• http://youtu.be/HaDNWZuYKfw

• Pressure & Henry’s law – solubility of a gas increases as pressure increases

Colligative Properties of Solutions

• Colligative properties depend on number of solute particles in a solution

• Vapor pressure lowering – – Vapor pressure:

– Adding a nonvolatile solute to a solution lowers the solvent’s vapor pressure

• Boiling point elevation –– Boiling point

– Because vapor pressure is lowered, boiling point increases

• Freezing point depression – solute particles interfere with attractive forces holding solvent particles together

• Osmotic Pressure– Osmosis –

– Additional pressure caused by water molecules that moved into the concentrated solution