Chem 170 1st Edition Lecture 12Outline of Last Lecture I. Quick Review: Vapor Pressure, Boiling PointII. Classification of Solidsa. Types of Crystalline Solidsi. Unit Cells of Crystalline SolidsOutline of Current Lecture I. SolutionII. Concentration UnitsIII. EntropyCurrent LectureChapter 13 – SolutionsA solution is homogenous throughout. A solute is dissolved inside a solvent. If the solvent is water then the solution is an aqueous solution. If the solute all dissolves then it is an “unsaturated solution”. If solute is added to the point that the solute does not dissolve any more then it is a “saturated solution”. “Supersaturated” means that there is more solute added than the limit. Solubility is the amount of solute that can be dissolved.Concentration Units:Molarity(M)=moles ofsolutelitersof solutionex. If there was 0.675g of NaCl in water and the total amount of solution is 250 mL, then what is the molarity?M=0.675 g(1 mol58 g)0.250 L=0.046 molMolality(m)=moles of solutekg of solventThis equation is useful, because it is not temperature dependent.Mole fraction(Xi)=molesitotal molesPercent by mass=mass solutetotal mass×100The “×100” means parts per hundred, so if we were looking for parts per million (ppm) then we would ×106.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.ex. If there was 10 cm3 of ethanol (ρ=0.789 g/cm3) and enough water was added to makea 100 cm3 solution with a density of 0.982 g/cm3.1. What is the percent of ethanol by volume?10 cm3100 cm3× 100=10 %2. What is the percent of ethanol by weight?10 cm3(0.7899 g1cm3)100 cm3(0.982 g1cm3)× 100=8.03 %3. What is the mass per volume percentage?10 cm3(0.789 g1cm3)100 cm3× 100=7.89 %4. What is the molarity?10 cm3(0.789 g1 cm3)(1mol46.06)=0.171 mol100 cm3(1 L1000 mL)=0.10 L0.171mol0.10 L=1.71 M5. What is the molality?10 cm3(0.789 g1 cm3)(1 mol46.06 g)10 cm3(0.789 g1cm3)−100 cm3(0.982 g1 cm3)=0.171 mol90.3 g(1 kg1000 g)=1.89 m6. What is the mole fraction?10 cm3(0.7891 cm3)(1mol46.06 g)10 cm3(0.7891 cm3)(1 mol46.06 g)+100 cm3(0.982 g1 cm3)(1 mol18 g)=3.3 %7. What is the ppm?7.89 g98.2× 106=80346 ppmEntropy (S) is a measure of disorder. The greater the degree of randomness or disorder in a system, the greater the entropy of a system.ex. NaCl a crystalline solid is dissolved in water. −¿+¿+Cl¿NaCl(s)→ Na¿endothermic: ΔH>0−¿+ H2O+¿+Cl¿Na¿endothermic: ΔH>0NaCl settles down by solvation exothermic ΔH<0total is endothermic ΔH<0ΔH= ΔHNaC l+ ΔHwater +
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