Questions
\(N_{2}O_{4(g)}\rightleftharpoons 2NO_{2(g)}\) \(K_{p}=3.0 at 70^{\circ C}\)
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A mixture of \(NO_{2(g)}\) and \(N_{2}O_{4(g)}\) is placed in a glass tube and allowed to reach equilibrium at \(70^{\circ C}\), as represented above. Which of the following best predicts how the partial pressures of the reacting species will be affected if a small amount of Ar(g) is added to the equilibrium mixture at constant volume?
(A) \(P_{NO_{2}}\) will decrease and \(P_{N_{2}O_{4}}\), will increase.
(B) \(P_{NO_{2}}\) will increase and \(P_{N_{2}O_{4}}\) will decrease.
(C) Both \(P_{NO_{2}}\) and \(P_{N_{2}O_{4}}\) will decrease.
(D) No change will take place.
▶️Answer/Explanation
Ans: D
When a small amount of an inert gas, such as argon (\(Ar(g)\)), is added to a system at constant volume, it doesn’t affect the partial pressures of the reacting species. This is because the addition of an inert gas does not alter the concentrations of the reacting species or the total pressure of the system.
In this case, the addition of \(Ar(g)\) to the equilibrium mixture will not impact the equilibrium concentrations of \(NO_2(g)\) and \(N_2O_4(g)\), nor will it change the total pressure of the system. Therefore, the partial pressures of the reacting species, \(P_{NO_2}\) and \(P_{N_2O_4}\), will remain unchanged.
Hence, the correct answer is (D) No change will take place.
Question
\(CO(l)(g)+2H_{2}(g)\rightleftharpoons CH_{3}OH(g) \) \(\Delta H<0\)
The synthesis of \(CH_3\)OH(g) from CO(g) and \(H_2\)(g) is represented by the equation above. The value of \(K_{c}\) for the reaction at 483 K is 14.5.
A mixture of CO(g) and\( H_{2}\)(g) is pumped into a previously evacuated 2.0 L reaction vessel. The total pressure of the reaction system is 1.2 atm at equilibrium. What will be the total pressure of the system if the volume of the reaction vessel is reduced to 1.0 L at constant temperature?
(A) Less than 1.2 atm
(B) Greater than 1.2 atm but less than 2.4 atm
(C) 2.4 atm
(D) Greater than 2.4 atm
▶️Answer/Explanation
Ans:B
Question
\(CO(g)+H_{2}O(g)\rightleftharpoons CO_{2}(g)+H_{2}(g)\) \( k_{c}=1.5\times 10^{3}\)
A 2.0 mol sample of CO(g) and a 2.0 mol sample of \(H_{2}\)O(g) are introduced into a previously evacuated 100. L rigid container, and the temperature is held constant as the reaction represented above reaches equilibrium. Which of the following is true at equilibrium?
(A) \([H_{2}O] > [CO] ~and ~[CO2] > [H2]\)
(B) \( [H_{2}O] > [H_{2}]\)
(C) \([CO_{2}] > [CO]\)
(D) \( [CO] = [H_{2}O]\) = \([CO_{2}]\) = \([H_{2}]\)
▶️Answer/Explanation
Ans:B
Question
\(2H_{2}S(g)+CH_{4}(g)\rightleftharpoons CS_{2}+4H_{2}(g)\) \( k_{c}=3.4\times 10^{-4}\)
A 0.10 mol sample of each of the four species in the reaction represented above is injected into a rigid, previously evacuated 1.0 L container. Which of the following species will have the highest concentration when the system reaches equilibrium?
(A)\( H_{2}\)S(g)
(B)\( CH_{4}\)(g)
(C) \(CS_{2}\)(g)
(D) \(H_{2}\)(g)
▶️Answer/Explanation
Ans:A
Question
\(CH_{3}OH(g) \rightarrow CO(g) + 2 H_{2}\)(g) \( \Delta H^{\circ}=+91KJ/mol_{rxn}\)
The reaction represented above goes essentially to completion. The reaction takes place in a rigid, insulated vessel that is initially at 600 K.
A sample of \(CH_{3}\)OH(g) is placed in the previously evacuated vessel with a pressure of \(P_1\) at 600 K. What is the final pressure in the vessel after the reaction is complete and the contents of the vessel are returned to 600 K?
(A) \(\frac{P_{1}}{9}\)
(B) \(\frac{P_{1}}{3}\)
(C) \({P_{1}}\)
(D) \(3{P_{1}}\)
▶️Answer/Explanation
Ans:D
Question
\(CH_{3}OH(g) \rightarrow CO(g) + 2 H_{2}\)(g) \( \Delta H^{\circ}=+91KJ/mol_{rxn}\)
The reaction represented above goes essentially to completion. The reaction takes place in a rigid, insulated vessel that is initially at 600 K.
A sample of \(CH_{3}\)OH(g) is placed in the previously evacuated vessel with a pressure of \(P_1\) at 600 K. What is the final pressure in the vessel after the reaction is complete and the contents of the vessel are returned to 600 K?
(A) \(\frac{P_{1}}{9}\)
(B) \(\frac{P_{1}}{3}\)
(C) \({P_{1}}\)
(D) \(3{P_{1}}\)
▶️Answer/Explanation
Ans:D
Question
\(N_{2}O_{4}\rightleftharpoons 2NO_{2}(g)\) \( K_{p}=3.0~at~70^{\circ}C \)
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A mixture of\( NO_{2}\)(g) and \(N_{2}O_{4}\)(g) is placed in a glass tube and allowed to reach equilibrium at 70°C, as represented above.
If \(P_{N_{2}0_{4}}\) is 1.33 atm when the system is at equilibrium at 70°C, what is \(P_{NO_{2}}\)?
(A) 0.44 atm
(B) 2.0 atm
(C) 2.3 atm
(D) 4.0 atm
▶️Answer/Explanation
Ans:A