chapter 15 chemical equilibrium
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0. Chapter 15 Chemical Equilibrium. 2NO (g) + O 2 (g) 2NO 2 (g). 0. What is Kp in terms of Kc for the following reaction ?. K p = K c RT K p = K c /RT K p = K c R/T K p = Kc K p = Kc/(RT) 2. 2NO (g) + O 2 (g) 2NO 2 (g). - PowerPoint PPT PresentationTRANSCRIPT
Chapter 15Chemical Equilibrium
What is Kp in terms of Kc for the following reaction ?
1. Kp = KcRT
2. Kp = Kc/RT
3. Kp = KcR/T
4. Kp = Kc
5. Kp = Kc/(RT)2
2NO (g) + O2 (g) 2NO2 (g)
What is Kp in terms of Kc for the following reaction ?
1. Kp = KcRT
2. Kp = Kc/RT
3. Kp = KcR/T
4. Kp = Kc
5. Kp = Kc/(RT)2
2NO (g) + O2 (g) 2NO2 (g)
What is the correct equilibrium constant expression for the reaction:
P4 (s) + 6Cl2 (g) 4PCl3 (l)
What is the correct equilibrium constant expression for the reaction:
P4 (s) + 6Cl2 (g) 4PCl3 (l)
Which accurately reflects the changes in concentration that will occur if O2 is added to disturb the equilibrium?
[NO] [O2] [NO]
1. Increase Increase Increase
2. Increase Increase Decrease
3. Decrease Decrease Decrease
4. Decrease Decrease Increase
5. Decrease Increase Increase
2NO (g) + O2 (g) 2NO2 (g)
NO NO2
Which accurately reflects the changes in concentration that will occur if O2 is added to disturb the equilibrium?
[NO] [O2] [NO]
1. Increase Increase Increase
2. Increase Increase Decrease
3. Decrease Decrease Decrease
4. Decrease Decrease Increase
5. Decrease Increase Increase
2NO (g) + O2 (g) 2NO2 (g)
NO NO2
Which of the following will result in an equilibrium shift to the right?
1. Increase temperature/increase volume
2. Increase temperature/decrease volume
3. Decrease temperature/increase volume
4. Decrease temperature/decrease volume
5. None of the above
PCl3 (g) + Cl2 (g) PCl5 (g) H° = -87.9 kJ/mol
PCl5
Which of the following will result in an equilibrium shift to the right?
1. Increase temperature/increase volume
2. Increase temperature/decrease volume
3. Decrease temperature/increase volume
4. Decrease temperature/decrease volume
5. None of the above
PCl3 (g) + Cl2 (g) PCl5 (g) H° = -87.9 kJ/mol
PCl5
What is the value of Kc for the reaction?
1. Kc = 1/(5.0 x 1018)1/2
2. Kc = 1/(2.5 x 1018)
3. Kc = -(5.0 x 1018)/2
4. Kc = -(5.0 x 1018)1/2
5. Kc = 2/(5.0 x 1018)1/2
2CO(g) + O2(g) 2CO2(g) Kc = 5.0 x 1018 at 25 °C
CO2(g) CO(g) + 1/2 O2(g) Kc = ?? at 25 °C
What is the value of Kc for the reaction?
1. Kc = 1/(5.0 x 1018)1/2
2. Kc = 1/(2.5 x 1018)
3. Kc = -(5.0 x 1018)/2
4. Kc = -(5.0 x 1018)1/2
5. Kc = 2/(5.0 x 1018)1/2
2CO(g) + O2(g) 2CO2(g) Kc = 5.0 x 1018 at 25 °C
CO2(g) CO(g) + 1/2 O2(g) Kc = ?? at 25 °C
For the gas-phase reaction A Bthe forward reaction rate is 3.0 104 s1 and the reverse reaction rate is 1.5 102 s1. What is the value of the equilibrium constant, Keq?
1. 0.022. 503. 0.0004
4. 2500
Correct Answer:
r
fc k
kK
0.021.5x10
3x102-
-4
cK
1. 0.022. 503. 0.0004
4. 2500
1. Homogenous
2. Heterogeneous
Does the following reaction represent a homogenous or a heterogenous equilbrium?
C(s) + CO2(g) 2 CO(g)
Correct Answer:
This is definitely a heterogeneous equilibrium because the reactants and products exist in two different phases, the solid and gaseous states.
1. Homogenous
2. Heterogeneous
Which of the following is the correct Keq for the equilibrium equation below?
2 Ag(s) + Zn2+(aq) 2 Ag+(aq) + Zn(s)
Correct Answer:
1. Keq = ___________
2. Keq = ___________
3. Keq = ___________
[2Ag+][Zn]
[Ag+]2[Zn]
[2Ag][Zn2+]
[Ag]2[Zn2+]
[Ag+]2
[Zn2+]
4. Keq = _________
5. Keq = _________[Zn2+]
[Ag+]2
[Zn2+]
[2Ag+]
Correct Answer (cont.):
Remember the equilibrium constant expression is given in terms of concentrations of products (raised to the exponent of their coefficients) divided by concentrations of reactants (raised to the exponent of their coefficients). Pure solids, liquids, and solvents are not included in the expression.
ba
dc
eqKBA
DC
For the following hypothetical reaction:
2 Y(aq) + 3 Z(aq) A(aq)
Calculate Keq given the following equilibrium concentrations: [A] = 0.50 M, [Y] = 0.10 M, [Z] = 1.0 M
1. 2.52. 5.03. 0.40
ba
dc
eqKBA
DC3. 0.025
4. 50.
32
1.00.10
0.50eqK
Correct Answer:
.500.01
0.50eqK
1. 2.52. 5.03. 0.404. 0.0255. 50.
For the following hypothetical reaction:
2 X(g) + Y(g) A(g)Keq = 250. At a point during the reaction, the concentrations are [A] = 1.0 M, [X] = 0.50 M, and [Y] = 0.10 M. How will the reaction proceed to achieve equilibrium?
1. From left to right (toward products)
2. From right to left (toward reactants)
3. Already at equilibrium
Correct Answer:
0.100.50
1.0 2
cK
40cKBecause Kc < Keq, the reaction will shift from reactants toward products to achieve equilibrium.
1. From left to right (toward products)
2. From right to left (toward reactants)
3. Already at equilibrium
For the following hypothetical reaction:
Y(g) + Z(g) 2 A(g)Keq = 4.0 102. Given that, what is the value of Keq for the reaction:
4 A(g) 2 Y(g) + 2 Z(g)
1. 25
2. 5.0
3. 0.016
4. 6.3 102
Correct Answer:
The second equation is twice the first and reversed. Thus, Keq of the second equation is related to the first as shown below:
2221
2 )100.4(
11
xKK
22 103.6 xK
1. 25
2. 5.0
3. 0.016
4. 6.3 102
The following reaction is at equilibrium:N2(g) + 3 H2(g) 2 NH3(g)
If we remove NH3(g), in what direction will the reaction move to reestablish equilibrium?
1. From left to right (toward products)
2. From right to left (toward reactants)
3. No change in equilibrium
Correct Answer:
If [NH3] is decreased, to return to equilibrium, more NH3 must be produced from the reactants. Thus, the reaction shifts from the reactants to the products.
1. From left to right (toward products)
2. From right to left (toward reactants)
3. No change in equilibrium
The following reaction is at equilibrium:
N2(g) + 3 H2(g) 2 NH3(g)If we increase the volume while holding the temperature constant, in what direction will the reaction move to reestablish equilibrium?
1. From left to right (toward products)
2. From right to left (toward reactants)
3. No change in equilibrium
Correct Answer:
Increasing the volume causes a shift in the equilibrium in the direction that produces more gas molecules, in this case on the reactants side.
1. From left to right (toward products)
2. From right to left (toward reactants)
3. No change in equilibrium
The following reaction is at equilibrium:
N2(g) + O2(g) 2 NO(g)
If we increase the pressure, in what direction will the reaction move to reestablish equilibrium?
1. From left to right (toward products)
2. From right to left (toward reactants)
3. No change in equilibrium
Correct Answer:
The number of gas molecules on both sides of the equation are equal; thus, changing the pressure will not change the equilibrium position.
1. From left to right (toward products)
2. From right to left (toward reactants)
3. No change in equilibrium
The following reaction is at equilibrium:N2(g) + O2(g) 2 NO(g)
H° = +180.8 kJ. In what direction will the reaction move to reestablish equilibrium if the temperature is decreased?
1. From left to right (toward products)
2. From right to left (toward reactants)
3. No change in equilibrium
Correct Answer:
As the temperature is lowered, equilibrium will shift to the side of the equation that produces heat. Thus, for an endothermic reaction, the equilibrium shifts from right to left toward the reactants.
1. From left to right (toward products)
2. From right to left (toward reactants)
3. No change in equilibrium