Download Chemistry Exam: Solubility, Equilibria, and Thermodynamics - Prof. Eric Glendening and more Exams Chemistry in PDF only on Docsity!
Name ______________________________________
Chem 106 April 20, 2007
Fourth Hour Exam
Potentially Useful Information:
R = 0.08206 L atm/mol K = 8.314 J/mol K โ G = โ G^0 + RT ln Q
โ G = โ H โ T โ S โ G^0 =โ RT ln K R
S
R T
H
K
ln
- (8 pts) Consider the following compounds. (i) Circle the compound that has the highest solubility in water. (ii) Cross out the compound that has the lowest solubility.
MgF 2 ( K sp = 6.4ร10โ9) CaSO 4 ( K sp = 6.1ร10โ5)
AgOH ( K sp = 2.0ร10โ8) PbBr 2 ( K sp = 4.6ร10โ6)
- (8 pts) Calculate the molar solubility of BaF 2 ( K sp = 1.7ร 10 โ^6 ) in a solution containing 0.10 M NaF.
molar solubility = ___________
- (8 pts) Explain, using balanced chemical equations, how the solubility of limestone (CaCO 3 ) is influenced by acid solutions. (No calculations here!)
- (8 pts) What is the minimum concentration of Fโ^ required to ensure that the concentration of Pb 2+^ remains below 1.0ร10 โ6^ M in a water sample? ( K sp = 3.6ร10 โ8^ for PbF 2 .)
[Fโ^ ] = ___________
- (18 pts) โ G^0 is 2.60 kJ/mol for the reaction H 2 ( g ) + I 2 ( g ) 2 HI( g ) at 298 K.
(a) Calculate the free energy of formation (โG (^) f^0 ) for HI( g ) at 298 K.
โG (^) f^0 = ___________
(b) Calculate K P at 298 K.
K P = ___________
(c) Calculate โ G at 298 K when the partial pressures of H 2 , I 2 , and HI are 1.00, 0.75, and 0.50 atm, respectively.
โ G = ___________
(d) Is this reaction, given the initial conditions of part (c), spontaneous or non-spontaneous? In what direction does the reaction proceed?
(e) Is this reaction spontaneous under standard conditions?
(f) What is โ G at equilibrium?
โ G = ___________
- (7 pts) For vaporization of mercury, Hg( l ) Hg( g ), โ H^0 is 61.3 kJ/mol and โ S^0 is 98.84 J/mol K. At what temperature is the system at equilibrium under standard conditions (assuming โ H^0 and โ S^0 do not depend on T)?
T = ___________
What do we call this temperature? ____________________________
- (18 pts) Au dissolves in aqua regia, a mixture of hydrochloric and nitric acids. The unbalanced chemical equation is:
Au( s ) + NO 3 โ^ ( aq ) + Cl โ^ ( aq ) AuCl 4 โ ( aq ) + NO 2 ( g )
(a) Write the balanced reduction half-reaction.
(b) Write the balanced oxidation half-reaction.
(c) Write the net reaction.
(d) The reducing agent is ___________; the oxidizing agent is ___________;
the species that gains electrons is ______________.
