Chem 1220 Week 3/7/16
Chem 1220 Week 3/7/16 Chem 1220(Chemistry, Dr. Clark, General Chemistry)
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Chem 1220(Chemistry, Dr. Clark, General Chemistry)
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This 4 page Class Notes was uploaded by Phillip Fishbein on Saturday March 12, 2016. The Class Notes belongs to Chem 1220(Chemistry, Dr. Clark, General Chemistry) at 1 MDSS-SGSLM-Langley AFB Advanced Education in General Dentistry 12 Months taught by Dr. Clark in Winter 2016. Since its upload, it has received 13 views. For similar materials see General Chemistry in Chemistry at 1 MDSS-SGSLM-Langley AFB Advanced Education in General Dentistry 12 Months.
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Date Created: 03/12/16
Chapter 17: Titrations and Solubility Basically acid-base equilibria and solubility investigations K sptting introduced Typical Titration Setup (Acid-Base) o Strong base in buret o Acid in beaker Break titrations into 4 regions o Initial pH o Between initial pH and equivalence point o Equivalence point – equal moles of titrant and analyte (base and acid, respectively) o Post equivalence point Weak Acid and Strong Base o Only the same calculations for pH in post equivalence o Use equilibriums constants and Henderson-Hasselbalch equation Kbfor equivalence point Indicators o Change color based on acid or base form of indicator species o If pH = pK a equal amounts base and acid form of indicator Solubility-Product Constant K sp o New equilibrium constant utilizing concentration o Involves only products of dissolving a salt Products are the only thing in solution Salt on reactant side is a solid, therefore not involved in the sp expression o Used to find: Molar solubility Gram solubility Concentration of ions in solution Predict formation of a precipitate (Q and K ) sp o Molar Solubility The number of moles of salt that dissolve in solution Higher K sppically shows higher molar solubility WARNING: Keep track of the number of each species that appears through dissolution!!!! (USE CHEMICAL EQUATION) Factors that Affect Solubility o Common ions Adding soluble salts with common ions to the species of interest, the solubility of the substance decreases Similar to discussion of buffers Can “neglect x” if Ksps really small compared to concentration of common ion o pH of the solution Changing pH may remove a weak acid or base that resides in the salt Removes product, drives reaction to the right (Le Chatelier’s Principle) Increases solubility o Presence of complexing agents A large charge that attracts Lewis base to exhibit complex bonding Called “coordinating the cation” i.e. Iron (III) surrounded by 6 water molecules New constant! K f Typically rather large Tend to favor formation of complex ions Removes the ion forming the complex Drives solubility to the right (Le Chatelier’s Principle) Increases solubility Can get all of solid to dissolve through formation of complex ions Chapter 19: Chemical Thermodynamics Spontaneous Reactions o Some are exothermic o Some are endothermic o New idea of entropy to determine whether a reaction is spontaneous or not Spontaneity o The measure of how spontaneous a process is o Spontaneous process occur without outside work o Spontaneous process occur in a definite direction o The reverse of a spontaneous process is not spontaneous Can reverse process with work o Depends on temperature o Not related to kinetics Entropy o Thermodynamic function o Related to number of different equivalent energy states or spatial arrangements a system may be found o Energy and the particles of matter “spread out” o Rudolf Clausius 2 ndLaw of Thermodynamics Introduced Entropy Studied steam engines and how they work Change in entropy is the heat divided by the temperature q ∆ S= ,q=heat ,T=temperature,S=entropy/spontaneity T Units of Joules per Kelvin (J/K) Explains transfer of heat from hot to cold ∆ S =∆ S +∆S >0 total sys surrounding o Ludwig Boltzmann Founding contributions in statistical thermodynamics Advocated atom theory Molecules have many equally possible microstates for the system to occur in n W=2 (¿of microstates) Many microstates correspond to an overall macrostates Macrostates are macroscopic observations Entropy measures the “spreading out” of energy in microstates 23 S=k∗ln W ),k=1.381∗10 J/K k = Boltzmann’s constant Gas constant divided by Avogadro’s number Enthalpy is an extensive property o Effecting Enthropy Volume Larger = higher entropy Number of particles More particles = higher entropy Temperature changes Higher temperature = higher entropy Arrangement of particles Weaker bonds = higher entropy More atoms = higher entropy o Not as much as more particles Molar Mass Larger mass = higher entropy o Motion of particles Translational Moving from one point to another Vibrational Shortening and lengthening of bonds, including changes in bond angle Rotational Spinning around an axis through the particle o State of matter can restrict particle motion 0 0 0 o ∆ S =∑ nS products− ∑ mS (reactants) o Josiah Willard Gibbs Theoretical basis for chemical thermodynamics
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