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Chem 17 Post Lab 1Experiments 1 3

15 February 2015Experiment 1: Colligative Properties of SolutionsSolution solute: dispersed component or inner phasesolvent: dispersing medium or outer phase

Note: a solution will always have a lower VP, lower FP and higher BP compared to a pure solventExperiment 1: Colligative Properties of SolutionsTypes of Disperse SystemsThe term "Disperse System" refers to a system in which one substance (the dispersed phase) is distributed, in discrete units, throughout a second substance (the continuous phase or vehicle).Each phase can exist in solid, liquid, or gaseous state .

Experiment 1: Colligative Properties of SolutionsTypes of Disperse Systems Medium/Phase Dispersed phaseGas Liquid Solid

GasNone Liquid aerosolSolid aerosol (All gases are mutually (fog, hair sprays)(smoke cloud, airmiscible) particles) LiquidFoam Emulsion Sol (whipped cream, (milk (blood shaving cream)mayonnaise) pigmented ink)

Solid Solid foam Gel Solid sol (aerogel, pumice(agar, gelatine(jewel, gemstone) polystyrene foam) jelly, opal)Experiment 1: Colligative Properties of SolutionsTypes of Disperse Systems

True solution< 1 nm

Heterogenous dispersion> 500 (1000) nmColloid dispersion1 500 (1000) nmheterogenous systems (blood, milk)microheterogenous system (plasma, macromolecular solutions)homogenous systems, salt, acid and base solutions

Experiment 1: Colligative Properties of SolutionsColligative Properties: properties that depend entirely on the amount of solute, not on its identity, present in a solution

VP lowering VP: P exerted by the vapor in equilibrium with its condensed phase.

Experiment 1: Colligative Properties of Solutions2. FP depression FP: T at which the liquid and the solid phase are at equilibrium

3. BP elevation BP: T at which the VP of of a liquid is equal to the barometric pressure

Experiment 1: Colligative Properties of Solutions4. Osmotic P the difference in the VP of the pure solvent and the solution of the solute in that solvent separated by a semi- permeable membraneOsmosis passage of solvent (water), from low to high concentration through a semi- permeable membrane

Experiment 1: Colligative Properties of SolutionsSample problemsCalculate the FP and BP of a soln of 383g glucose dissolved in 400g water.What is the boiling point of a soln of 30.20g ethylene glycol in 88.40 phenol?Calculate the molar mass of a noneletrolyte that lowers the FP of 25g of water to -3.9 C when 4.27g of substance is dissolved in the water.Experiment 1: Colligative Properties of SolutionsSample problems4. How much glucose per liter should be used for an intravenous solution to match the 7.65 atm at 37 C osmotic pressure of blood? 5. What is the osmotic pressure of a solution prepared by adding 13.65 g of sucrose (C 12 H 22 O 11 ) to enough water to make 250 mL of solution at 25 C?

Experiment 2: Heat Effects and CalorimetryHeat, q transfer of energyCalorimetry the process of measuring the heat flow (H) using a calorimeter2 types of calorimeterCoffee- cup calorimeter constant PBomb calorimeter constant VExperiment 2: Heat Effects and CalorimetryHeat Capacity - amount of heat required to raise the temperature of an object or substance one degree

Experiment 2: Heat Effects and CalorimetryHeat of neutralization (Hn) - occurs when one equivalent of an acid and one equivalent of a base undergo a neutralization reaction to form water and a salt

Experiment 2: Heat Effects and CalorimetryHeat of solution - enthalpy change associated with the dissolution of a substance in a solvent at constant pressureEndothermic reaction T of the system increasesExothermic reaction T of the universe increases

Experiment 2: Heat Effects and CalorimetryHeat of combustion - energy released as heat when a compound undergoes complete combustion with oxygen under standard conditions, measured by a bomb calorimeterExperiment 2: Heat Effects and CalorimetrySample problems300 grams of ethanol at 10 C is heated with 14640 Joules of energy. What is the final temperature of the ethanol? specific heat of ethanol is 2.44 J/gCIt takes 487.5 J to heat 25 grams of copper from 25 C to 75 C. What is the specific heat in Joules/gC? Experiment 2: Heat Effects and CalorimetrySample problems

Experiment 3: Chemical KineticsChemical kinetics study of rates and mechanisms of chemical reactionsFactors that affect reaction ratesnature of reactantsconcentration of reactantstemperaturecatalystsurface areaExperiment 3: Chemical Kineticsnature of reactants homogeneity of the reactants help dictate the rate of the reaction, acid/base reactions, the formation of salts, and ion exchange are fast reactions while complex formation reactions are slow

iron + hydrochloric acid vs iron + acetic acid Experiment 3: Chemical Kineticsconcentration of reactants reactions are due to collisions of reactant species, higher concentration means faster reaction

temperature higher T, higher KE, higher chances of collisions; therefore, faster reaction

effect of surface area powdered samples or reactants are always faster

Experiment 3: Chemical Kineticspresence of catalyst a catalyst is a substance that participates in a chemical reaction and increases the reaction rate without undergoing a net chemical change itself

Experiment 3: Chemical KineticsOrder of Reactions - defined as the index, or exponent, to which its concentration term in the rate equation is raised

Zero order the reaction rate is independent of the concentration of the reactant1st order reaction rate depends on a single reactant ie. radioactive decay reactions2nd order reaction rate depends on 2 reactants

Experiment 3: Chemical KineticsOrder of Reactions

Experiment 3: Chemical KineticsMethod of initial rates

Experiment 3: Chemical KineticsTheoretical models for Chemical Kinetics1. Collision Theory only a fraction of the collisions among gaseous molecules lead to chemical reaction

Experiment 3: Chemical KineticsTransition State Theory a hypothetical specie (activated complex) is believed to exist in a transitory state (transition state) that lies between the reactants and the products

Experiment 3: Chemical KineticsTransition State Theory