SI Chem 178
Thursday Jan 31st
Focus on Ch 15, Look at 16
Leader: Emily
Warm Up/Review (Conceptual):
15.19: Can Kc be negative? Why or why not?
Visual problems 15.4, 7, 8, 10 (Discuss with a partner. Do you understand all of these
concepts?) These were highlighted for the quiz.
What is Q? What do the following situations mean?
Q=K
Q>K
Q<K
Problems:
15.27 (Similar to assigned 15.28) (Concept: Kc combination)
The following equilibria were attained at 823 K.
CoO(s) + H2(g)   Co(s) + H2O(g) Kc=67
CoO(s) + CO(g)   Co(s) + CO2(g) Kc=490
Using these, find the Kc for: H2(g) + CO2(g)   CO(g) + H2O(g) @823 K
15.46 (Concept: Kp, product/reactant shift, Q)
N2(g) + 3H2(g)   2NH3(g) (Kc= 4.51*10^-5 at 450 Deg C)
For each of the following mixtures, determine if it is at equilibrium or if products/reactants
will be favored.
a) 98 atm NH3, 45 atm N2, 55 atm H2
b) 57 atm NH3, 143 atm N2, 0 atm H2
c) 13 atm NH3, 27 atm N2, 82 atm H2
15.55 (Concept: Heterogeneous mixtures, concentration calculation)
Consider the following: CaSO4(s)   Ca2+(aq) + SO4 2- (aq) Kc @ 25C = 2.4*10^-5
a) Given a saturated solution of Ca2SO4, what are the equilibrium concentrations of Ca2+
and SO4 2- ?
b) If the solution above has a volume of 1.4L, what is the mass of CaSO4 needed to create
this equilibrium? Saturated solution is 4.9*10^-3M. MM=136.14
15.63 (Similar to assigned 15.62, Le Chatelier’s Principles)
You are observing a gas phase exothermic reaction, how does the equilibrium constant
change if you….
a) Remove a reactant?
b) Remove a product?
c) Decrease the volume?
d) Decrease the temp?
e) Add a catalyst?
Preview:
Acid/Base Review Ch 16 (Look over 16.1, 16.2)
a) What are the conjugate bases of HClO4, H2S, PH4+, and HCO3-
b) What are the Conjugate acids of HSO3- , F- , PO4 3- , and CO ?
c) What would you hypothesize about the Kc of the dissolution of a strong acid/base?