Chapter 141 Solutions and Their Behavior Chapter 14

2 The Solution Process Solution - A homogeneous mixture composed of a solute and a solvent. Solute – The substance which is dissolved. Solvent – The substance which acts as the dissolving medium.

Chapter 143 Saturated Solutions and Solubility Mole Fraction, Molarity, and Molality Qualitative Terms: Dilute Solution – A solution in which additional solute may be dissolved. Saturated Solution – A solution in which no more solute may be dissolved. Supersaturated Solution – A solution in which more solute is dissolved than in a saturated solution. Solubility - amount of solute required to form a saturated solution.

Chapter 144 Ways of Expressing Concentration Definitions:

Chapter 145 Ways of Expressing Concentration Mole Fraction, Molarity, and Molality Mole Fraction Molarity

Chapter 146 Ways of Expressing Concentration Mole Fraction, Molarity, and Molality Molality (m) – moles of solute per kilogram of solution

Chapter 147 The Solution Process Liquids Dissolving in Liquids Miscible liquids - Mix in any proportions. Immiscible liquids - Do not mix.

Chapter 148 The Solution Process Liquids Dissolving in Liquids “Like Dissolves Like” Polar molecules will dissolve in polar solvents. Non-polar molecules will dissolve in non-polar solvents.

Chapter 149 The Solution Process Solids Dissolving in Liquids “Like Dissolves Like” Still true but less effective (i.e. there are exceptions) Also, many dissolution processes are endothermic. A classic example is Ammonium nitrate in water. A classic exception is Sulfuric acid in water.

Chapter 1410 The Solution Process Heat of Solution For a solid to dissolve: Energy must be supplied to separate the ions in the crystal lattice: -  H lattice Energy is evolved individual items are surrounded by the solvent:  H hydration  H solution = ( -  H lattice +  H hydration )

Chapter 1411 Factors Affecting Solubility Temperature Effects

Chapter 1412 Factors Affecting Solubility Pressure Effects Solubility of a gas in a liquid is a function of the pressure of the gas. The higher the pressure, the greater the solubility.

Chapter 1413 Factors Affecting Solubility Pressure Effects Henry’s Law – The solubility of a gas increases in direct proportion to its partial pressure above the solution. S g - solubility of gas P g - the partial pressure of the gas k H - Henry’s law constant.

Chapter 1414 Factors Affecting Solubility Temperature Effects

Chapter 1415 Factors Affecting Solubility Temperature Effects The solubility of a gas is greater in a cold solvent. The dissolution of a gas in water is an exothermic process.

Chapter 1416 Colligative Properties Properties of a solution which depend on quantity of solute molecules. Solutions formed with a nonvolatile solute will: have lower vapor pressure lower freezing point higher boiling point

Chapter 1417 Colligative Properties Boiling-Point Elevation

Chapter 1418 Colligative Properties Raoult’s Law Raoult’s Law – The equilibrium vapor pressure of the solvent over the solution is directly proportional to the mole fraction of the solvent in the solution P solvent - vapor pressure of the solvent in the solution P  solvent - vapor pressure of the pure solvent  solvent - the mole fraction of solvent

Chapter 1419 Colligative Properties Change in Vapor Pressure  P solvent - vapor pressure of the solvent in the solution P  solvent - vapor pressure of the pure solvent  solute - the mole fraction of solute

Chapter 1420 Colligative Properties Boiling-Point Elevation As the vapor pressure of a solution decreases, the boiling point increases. Recall, a solvent boils when its’ vapor pressure equals the atmospheric pressure.

Chapter 1421 Colligative Properties Boiling-Point Elevation K bp - Molal boiling-point elevation constant m – solution molality  T bp – boiling point change

Chapter 1422 Colligative Properties Freezing-Point Depression Just as the boiling point is raised, the freezing point is lowered.

Chapter 1423 Colligative Properties Freezing-Point Depression K fp - Molal freezing-point depression constant m – solution molality  T fp – freezing point change

Chapter 1424 Colligative Properties F.Pt. and B.Pt. Change with Ionic Solutes The previous equations assumed molecular solids –example, sugar (C 6 H 12 O 6 ) Recall that colligative properties are a function of the number of bodies in the solution.

Chapter 1425 Colligative Properties F.Pt. and B.Pt. Change with Ionic Solutes F. Pt. depression and B. Pt. equations must be modified to account for this. K bp - Molal boiling-point elevation constant m – solution molality  T bp – boiling point change i – van Hoff factor

Chapter 1426 Colligative Properties F.Pt. and B.Pt. Change with Ionic Solutes K fp - Molal freezing-point depression constant m – solution molality  T fp – freezing point change i – van Hoff factor

Chapter 1427 Colligative Properties Molar Mass Determination The molar mass (molecular weight) can be determined by observing the freezing point change to a solution in which a know quantity of non-volatile solute has been added.

Chapter 1428 Colligative Properties Osmosis The net movement of solvent through a semi-permeable membrane from a dilute to a concentrated solution.

Chapter 1429 Colligative Properties Osmosis Eventually the pressure difference between the arms stops osmosis.

Chapter 1430 Colligative Properties Osmosis Osmotic pressure(  ) - The pressure required to stop osmosis: c - molarity of the solution R - gas constant ( L(atm)/mol(K)) T - temperature in Kelvin

Chapter 1431 Colloids Colloids are suspensions in which the suspended particles are larger than molecules but too small to drop out of the suspension due to gravity. Particle size: 10 to 2000 Å.

Chapter 1432 Colloids Tyndall effect: ability of a Colloid to scatter light. The beam of light can be seen through the colloid.

Chapter 1433 Homework 4, 8, 23, 28, 38,42, 52