CHEM 1120 Edition 1nd Lecture 2 Outline of Last Lecture I Syllabus Overview Outline of Current Lecture II Intro to Chapter III Intermolecular forces a Difference between intermolecular and intramolecular forces b 6 types of intermolecular forces c Gas and Solid solutions d Why do substances dissolve IV Heat of Solution a Equation Heat of solute Heat of solvent Heat of mixing V The Solution Process and Entropy a Why not all processes are exothermic b Saturated unsaturated and supersaturated solutions Current Lecture I II Intro to Chapter a Does NOT have to be a liquid to be a solution b Solvent most of solution what substance is being dissolved in c Solute least of solution what is being dissolved d How does a solution form Solvent pulls solute particles apart Called solvating e Competition between whether it wants to be dissolved or if it wants to stay with the crystal can go back and forth f At equilibrium no ions come back to the solid Intermolecular Forces a Intermolecular between DIFFERENT molecules b Intramolecular within a SINGLE molecule c Solution of A and B will form ONLY if A B attractions are comparable in strength to A A and B B attractions i If not they won t mix i e Water and oil d Attractive forces between the solute and solvent can be VERY STRONG i i e Melting point of NaCl is 801 degrees C but water will dissolve it at room temp ii When solvent is water called hydration These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute III IV e 6 types of intermolecular forces i Ion dipole strongest 40 600 Measured in kJ mol Na H2O 1 Ion and dipole interact ii Hydrogen bonding 10 40 CH3OH H2O 1 Hydrogen bonds to N O F iii Dipole dipole 5 25 PH3 H2O 1 2 dipoles interacting iv Ion Induced Dipole 3 15 Fe2 O2 in blood 1 Bring a charge next to something that doesn t have a dipole causes it to become a dipole Take charge away dipole will go away 2 Less common v Dipole Induced dipole 2 10 H2O O2 1 Less common 2 Similar to ion induced vi Dispersion Forces 05 40 C8H18 C6H14 1 At an instantaneous point molecule has a charge f Gas and Solid solutions i Gas gas infinitely soluble in each other ii Gas solid gasses dissolve in solids by filling holes iii Solid solid atoms may replace atoms called substitutional alloys or occupy holes called interstitial alloys g Why do substances dissolve 3 steps dissolving NaCl in water i Step 1 NaCl crystals separated into ions endothermic process positive 1 Separating ions takes work ii Step 2 Water molecules create holes to accommodate Na and Cl ions endothermic process positive 1 Separating the water molecules also takes work iii Step 3 the Na and Cl ions enter the holes exothermic process negative Heat of Solution a Heat of solute Heat of solvent Heat of mixing Heat of solution i Heat of solution is NOT predictable or ii Heat of solute Heat of solvent Heat of mixing Heat of solution is iii Heat of solute heat of solvent Heat of mixing Heat of solution is iv Technology in heat and cold pads mix two things endothermic cold pads exothermic heat pads The Solution Process and Entropy a Naturally expect objects to move towards lower energy MOST chemical processes Exothermic b Not all chemical processes exothermic i Systems tend toward a state of higher entropy S ii Covered more later in chapter 19 c Saturated solutions and solubility i Add more of a solute to a solvent and it dissolves UNSATURATED ii Add more and it crystalizes SUPERSATURATED 1 Very unstable iii At equilibrium SATURATED iv