Chem 112 Exam AID Course Pack

The acid and base dissociation constants for a

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Unformatted text preview: ulfide, Ga2S3. If we heat 2 mol of gallium and 2 mol of sulfur, what is the maximum number of moles of Ga2S3 that can be formed? a) b) c) d) e) 1/3 2/3 ½ 1 2 33. An ore contains 1.34% Ag2S, by mass. How many grams of this ore would have to be processed to obtain 1.00 g of pure silver, Ag? a) b) c) d) e) 74.6 g 85.7 g 107.9 g 134.0 g 171.4 g 34. What is the core charge on a Cl- ion? a) b) c) d) e) - 1 0 +7 +8 +17 35. The “nb” term in the van der Waals equation (see information sheet) allows for the fact that: a) b) c) d) e) real gases liquefy molecules in real gases have a finite mass molecules in real gases have a finite volume molecules in real gases attract each other molecules in real gases have dipole moments Ethan Newton & Barry Zhang for SOS Winter 2012 41 9.0 Chemical Equilibria Equilibrium: Defined as a dynamic balance of forward and reverse processes A chemical equilibrium must satisfy these: i) the system is closed ii) Shows no visible evidence of change iii) Reached through a spontaneous process. Properties of a system at equilibrium: there is a continuous exchange between reactants and products at the molecular level with out a change in concentration Caveat: Absence of observable change does not prove the existence of equilibrium because the reaction may just be really slow or a steady state may exist (where the products or reactants are being removed/added) The Equilibrium Constant: Note: Equilibrium constant will be obtained regardless of direction from which it was approached (when temperature is constant) We will focus on this general reaction formula where the capitals are molecules and the lowercase letters represent the molar coefficients: (*note the arrow represents a double headed equilibrium arrow) • The equilibrium constant is based on the fact that regardless of the original concentrations of A B C or D, the ratio of Products/Reactants is constant and this is known as the Law of mass action. • The equilibrium constant expression (Keq) is represented here: *AT EQUILIBRIUM! K eq = [products] [reactants] [C]c [D]d = [A]a [B]b Anything with a concentration of 1 is not included in the equilibrium expression (ex. NaCl(s) or H2O(l)) € • If K is large (ex 1000 or high...
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