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Chemistry, 7/e
Raymond Chang, Williams College

Chemical Equilibrium

Self Assessment A



1

The equilibrium constant Keq for a certain reaction will change if __________ changes.
A)pressure
B)time
C)volume
D)temperature
E)reactant concentrations
2

What is the relationship of the equilibrium constants for the following two reactions?
(1) 2 NO2(g) ----> N2O4(g);
(2) N2O4(g) ----> 2 NO2(g)
A)Keq of reaction (1) is the reciprocal of Keq of reaction (2).
B)Keq of reaction (2) is the reciprocal of Keq of reaction (1)
C)Keq of reaction (1) = Keq of reaction (2)
D)Answers A and B are both correct
E)There is no relationship between the Keqs of these reactions
3

What is the correct equilibrium constant expression for the following reaction? 2 Cu(s) + O2(g) ----> 2 CuO(s)
A)Keq = 1/[O2]2
B)Keq = [CuO]2/[Cu]2
C)Keq = [CuO]2/[Cu]2[O2]>
D)Keq = [O2]
E)Keq = 1/[O2]
4

Consider the reaction: 2 SO2(g) + O2(g) ----> 2 SO
A)5.78
B)1.73
C)2.27
D)0.37
E)None of the above
5

PCl5 dissociates according to the reaction: PCl5(g) ----> PCl3(g) + Cl2(g). One mole of PCl5 was placed in one liter of solution. When equilibrium was established, 0.5 mole of PCl5 remained in the mixture. What is the equilibrium constant for this reaction?
A)0.25
B)0.50
C)1.0
D)2.5
E)None of the above
6

At elevated temperatures, solid silicon reacts with chlorine gas to form gaseous SiCl4. At some temperature, the equilibrium constant for this reaction is 0.30. If the reaction is started with 0.10 mol of SiCl4 in a one-liter flask, how much Cl2 will be present when equilibrium is established?
A)0.18 mol
B)0.090 mol
C)0.030 mol
D)0.30 mol
7

Consider the reaction: CO2(g) + H2(g) ----> CO(g) + H2O(g), for which Kc = 0.64 at 900 K. If the initial CO2 and of H2 are each 0.100 M, what will be the equilibrium concentrations of each species after the reaction reaches equilibrium?
A)[CO2] = 0.044 M; [H2] = 0.044M; [CO] = 0.056 M; [H2O] = 0.056 M
B)[CO2] = 0.056 M; [H2] = 0.056 M; [CO] = 0.044 M; [H2O] = 0.044 M
C)[CO2] = 0.020 M; [H2] = 0.020 M; [CO] = 0.080 M; [H2O] = 0.080 M
D)[CO2] = 0.080 M; [H2] = 0.080 M; [CO] = 0.020 M; [H2O] = 0.020 M
E)None of the above
8

At some temperature, the reaction: 3 ClO- ----> ClO3- + 2 Cl- has an equilibrium constant Kc = 3.2 x 103. If the components of this reaction are mixed such that their initial concentrations are [Cl-] = 0.05 M; [ClO3-] = 0.32; and [ClO-] = 0.74, is the mixture at equilibrium, yes or no? If the mixture is not at equilibrium in which direction, left to right or right to left, will reaction occur so that the mixture can reach equilibrium?
A)There is not enough information given to answer this question
B)Yes, the mixture is at equilibrium now
C)No. Left to right
D)No. Right to left
9

Consider the following endothermic reaction: H2(g) + I2(g) ----> 2 HI(g). If the temperature is increased,
A)more HI will be produced
B)some HI will decompose, forming H2 and I2
C)the magnitude of the equilibrium constant will decrease
D)the pressure in the container will increase
E)the pressure in the container will decrease
10

Consider the following reaction at equilibrium: NO2(g) + CO(g) ----> NO(g) + CO2(g). Suppose the volume of the system is decreased at constant temperature, what change will this cause in the system?
A)A shift to produce more NO
B)A shift to produce more CO
C)A shift to produce more NO2
D)No shift will occur