Week 2 of notes after the first exam in gen chem 2
Week 2 of notes after the first exam in gen chem 2 chem 10061-001
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This 3 page Class Notes was uploaded by Matthew Goetz on Friday March 4, 2016. The Class Notes belongs to chem 10061-001 at Kent State University taught by David bowers in Summer 2015. Since its upload, it has received 42 views. For similar materials see general chemistry 2 in Chemistry at Kent State University.
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Date Created: 03/04/16
General Chemistry 2 Notes: Molality: Moles of solute/ kg of solvent Parts by mass: mass of solute/ mass of solution Parts by volume: volume of solute/ volume of solution Mole fraction: moles of solute/ mol of solute + mol of solvent Parts per million: (mass of solute/ total mass of solution) x 10 ^6 These are all important equations that will need to be known for the exam. Colligative Properties: Adding solutes to a solvent alters physical properties of that solvent. Vapor pressure reduction Boiling point elevation Freezing point depression Osmotic pressure changes These properties only depend on the # of solute particles that have dissolved. Therefore, it is important to remember solubility of compounds and salts. Solute’s presences lowers the mole fraction of the solvent and therefore the vapor pressure is reduced and less particles can leave the solution. Nonvolatile nonelectrolytic solutions: Vapor pressure lowers due to the fact that solute addition increases entropy. Vapor pressure exists in support of entropy and when the entropy is increased due to a solute’s presence the vapor pressure may decrease. Think of it this way: If you have to eat 3 hamburgers to be full, but you eat a lot of fries before you eat the burgers, you have to eat less burgers to be full! So, if the vapor pressure has to be a certain level to meet the required entropy, but the solute adds entropy, then the vapor pressure may decrease. Change in vapor pressure is shown by Raoult’s Law: X is the mole fraction of the solution P^o a is the vapor pressure of the pure solvent. Boiling point elevation occurs as well: Solution boils at a higher temperature. This process is shown by this equation… Kb is a constant that is given m is the molality of the solution Freezing point depression also occurs: A solution freezes at a lower temperature. This process is shown by the exact same equation above. Osmotic Pressure: This is the pressure required to block osmosis (π) The equation is π= mrt M is the molarity R is the constant .08206L per atm/mol x K T is the temperature in kelvins Colligative properties of volatile nonelectrolytic solutions: Volatility and vapor pressure of both are depressed. Strong electrolytic solutions: These involve dissociation of ions, so we must multiply every equation by the van’t Hoff factor. The van’t Hoff factor is merely: I = measured value for electrolytic solution/ expected value. Molarity x seconds is the speed of reactions. Chemical Kinetics: Study of reaction rates. 4 factors determine speed of a reaction: Concentration Physical states of the solution Temperature: Higher temps increase reaction rates. Presence of a catalyst: Lower activation energy. Reaction rate: Change in concentration / change in time. For reactions involving coefficients, use the equation: aA + bB yields cC + dD. The equations for this part are best acquired in class, for I haven’t the ability to type them properly….. Rate law expression: For instantaneous rates, Rate = k[A]^x[B]^y k is the rate constant x and y are the orders of reaction with respect to the reactants Rate law only includes reactions!!! Reaction orders are determined by experiment. First order reactions are when the rate of A is directly proportional to the concentration. So, if A doubles, then the concentration doubles as well. Second order reactions are when the rate is the square of the concentration. So, if A doubles, then the concentration quadruples. Or, if A triples, then the concentration is multiplied by 9. Zero order reactions are when the Rate has no effect on the concentration…… These reaction orders cannot be determined from balanced chemical equations.
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