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