7.2 Chapter 13 Solutions (6 per page)

7.2 Chapter 13 Solutions (6 per page) - 1 Chapter 13...

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Unformatted text preview: 25/02/2011 1 Chapter 13: Solutions and their Physical Properties Properties Objectives • Calculate concentration using different units. • Study thermodynamics of solution and solubilities of liquids, solids and gases in liquid solvents. • Understand the process of distillation: Raoult’s Law, azeotropes. • Calculate colligative properties of electrolyte and non-electrolyte solutions: freezing point, boiling point, osmotic pressure. Solution: A homogeneous mixture of two or more substances. 13-1 Types of Solutions • gaseous • Air: N 2 ,O 2 , Ar, CO 2 , Ne, CH 4 , He, Kr, H 2, Xe • liquid + 2 • Seawater: H 2 O, Cl- , Na + , SO 4 2 , Mg 2+ , Ca 2+ , K + , HCO 3- , Br- , Sr 2+ , Fl- • solid • red brass: Cu, Zn, Pb, Sn, Fe, Cd 13-2 Solution Concentration • Different measures of how much solute is dissolved in how much solvent. – small amount of solute: dilute – large amount of solute: concentrated 13-2 Solution Concentration • Mole Fraction ( ) – moles of solute ÷ total moles of solution – A =0.5 means half the molecules are A. • Molarity ( M=moles L-1 ) Molarity ( M moles L ) – moles of solute ÷ liters of solution • Molality ( m =moles kg-1 ) – moles of solute ÷ mass of solvent (kg) – not affected by thermal expansion/contraction of solvent • Others: see textbook 25/02/2011 2 13-3 Intermolecular Forces and the Solution process • Pure A has only A-A interactions. • Pure B has only B-B interactions. • A solution of A & B has A-A, B-B and A-B interactions. 13-3 Enthalpy of Solution dissociate solute mix solvent & solute dissociate solvent endothermic exothermic 13-3 Enthalpy of Solution • Overall change in enthalpy can be positive, negative, or close to zero. 13-3 Enthalpy of Solution dissociate solute mix solvent & solute dissociate solvent overall exothermic ∆ H < 0 forces between unlike molecules stronger than those between like molecules 13-3 Enthalpy of Solution • Forming a solution of water with pure mineral water with pure mineral acids (like H 2 SO 4 ) is highly exothermic. 13-3 Enthalpy of Solution • ALWAYS add acid to water, NOT water to acid. – the solution can get extremely hot extremely fast. – Water has high heat capacity. – Better to have boiling 10% acid solution than boiling 90% acid solution. 25/02/2011 3 13-3 Enthalpy of Solution dissociate solute mix solvent & solute dissociate solvent ∆ H 13-3 Ideal Solutions • ∆ H is close to zero when forces between like and unlike molecules are very similar. • These mixtures are called ideal solutions. benzene toluene 13-3 Enthalpy of Solution dissociate solute mix solvent & solute dissociate solvent overall endothermic ∆ H > 0 forces between unlike molecules weaker than those between like molecules • Dissolution of ammonium nitrate (NH 4 NO 3 ) in water is endothermic....
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This note was uploaded on 04/04/2011 for the course SCIENCE CHEM 120 taught by Professor Fenster during the Winter '11 term at McGill.

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7.2 Chapter 13 Solutions (6 per page) - 1 Chapter 13...

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