Equilibrium Supplement I
1. Characterize a system of gas molecules in a closed container at equilibrium with
respect to each of the following:
A) rates of the forward and reverse reactions.
B) the composition of reactants and products.
C) the total pressure in the container.
2. Distinguish between the terms equilibrium constant and reaction quotient.
3. There is only one value of the equilibrium constant for a particular system at a
particular temperature, but there is an infinite number of equilibrium positions. Explain.
4. Write equilibrium constant expressions, KC, or the reactions
A) 2NO(g) + O2(g)  2NO2(g)
B) Cu(s) + 2Ag+(aq)  Cu2+(aq) + 2Ag(s)
C) Ca(OH)2(s) + CO32-(aq)  CaCO3(s) + 2OH-(aq)
5. Write equilibrium constant expressions, KP, for the reactions
A) CS2(g) + 4H2(g)  CH4(g) + 2H2S(g)
B) HgO(s)  Hg(l) + ½ O2(g)
C) 2NaHCO3(s)  Na2CO3(s) + CO2(g) + H2O(g)
D) 3O2(g)  2O3(g)
6. At high temperature, elemental nitrogen and oxygen react with each other t oform
nitrogen monoxide:
N2(g) + O2(g)  2NO(g)
At a certain temperature an equilibrium mixture is found to contain the following
concentrations: [N2] = 0.041 M, [O2] = 0.0078 M, and [NO] = 4.7x10-4 M.
A) Calculate KC for this reaction.
B) Calculate KP for this reaction.
7. The reaction below is carried out at 25 oC:
2NOCl(g)  2NO(g) + Cl2(g)
At equilibrium, the following pressures are found: PNOCl = 1.20 atm, PNO = 1.25x10-2 atm,
and PCl2 = 3.00x10-1 atm.
Calculate KP for this reaction at 25 oC.
Answers
1: A) Forward and reverse reaction rates are equal; B) the concentrations of all reactants
and products remains constant; C) the pressure stays constant; 2: The equilibrium
constant is the value of the reaction quotient when the system is at equilibrium. ; 3: There
are an infinite number of combinations of reactants and products that will equal the
equilibrium constant when there values are substituted into the reaction quotient;
however, at a given temperature there is only on value of the equilibrium constant.;
4: A) [NO2]2/ [NO]2[O2]; B) [Cu2+]/[Ag+]2; C) [OH-]2/[CO32-];
5: A) PCH4PH2S2/PCS2PH24; B) PO20.5; C) PCO2PH2O; D) PO32/PO23
6: A) 6.9x10-4; B) 6.9x10-4; 7: 3.26x10-5
Borowski Spring 2001