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Exam 14: Chemical Equilibrium

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Question 51

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The equilibrium constants for the chemical reaction N₂(g) + O₂(g) 2NO(g) are K_P = 1.1 * 10^-3 and 3.6 * 10^-3 at 2,200 K and 2,500 K, respectively. Which one of these statements is true?

A) The reaction is exothermic, $\Delta$ Hº < 0.
B) The partial pressure of NO(g) is less at 2,200 K than at 2,500 K.
C) K_P is less than K_c by a factor of (RT) .
D) The total pressure at 2,200 K is the same as at 2,500 K.
E) Higher total pressure shifts the equilibrium to the left.

F) C) and D)
G) B) and E)

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Question 52

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The brown gas NO₂ and the colorless gas N₂O₄ exist in equilibrium, 2NO₂ N₂O₄. In an experiment, 0.625 mole of N₂O₄ was introduced into a 5.00 L vessel and was allowed to decompose until equilibrium was reached. The concentration of N₂O₄ at equilibrium was 0.0750 M. Calculate K_c for the reaction.

A) 7.5
B) 0.125
C) 0.0750
D) 0.10
E) 0.050

F) None of the above
G) B) and D)

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Question 53

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The data below refer to the following reaction: 2NO(g)+ Br₂(g) 2NOBr(g) Find the concentration of Br₂ when the system reaches equilibrium.

Consider the chemical reaction 2NH₃(g) N₂(g)+ 3H₂(g).The equilibrium is to be established in a 1.0 L container at 1,000 K, where K_c = 4.0 * 10^-2. Initially, 1,220 moles of NH₃(g)are present.Estimate the equilibrium concentration of N₂(g).

Consider the equilibrium equation C(s)+ H₂O(g)+ 2296 J CO(g)+ H₂(g).What will happen to the mass of carbon if we add gaseous water to the system?

Ethanol and acetic acid react to form ethyl acetate and water according to the following chemical equation: C₂H₅OH(l)+ CH₃COOH(l) CH₃COOC₂H₅(l)+ H₂O(l) When two moles each of ethanol and acetic acid are combined, equilibrium is reached when two-thirds of a mole of each of the reactants remains.Calculate the equilibrium constant for this reaction assuming total volume does not change during the course of the reaction.(Note: since water is not the solvent, but rather a product of the reaction, [H₂O] changes during the course of the reaction, so it should be included in the equilibrium constant expression.)

At 340 K, K_p = 69 for the reaction H₂(g) + I₂(g) 2HI(g) . 50.0 g of HI is injected into an evacuated 5.00-L rigid cylinder at 340 K. What is the total pressure inside the cylinder when the system comes to equilibrium?

What conditions are used in the Haber process to enhance the yield of ammonia? Explain why each condition affects the yield in terms of the Le Châtelier principle.

The following reactions occur at 500 K.Arrange them in order of increasing tendency to proceed to completion (least completion $\rarr$ greatest completion) .

Solid ammonium hydrogen sulfide is introduced into a 2.00-L flask, and the flask is sealed.If this solid decomposes according to the equation NH₄HS(s) NH₃(g) + H₂S(g) , K_p = 0.108 at 25°C, What is the minimum mass of ammonium hydrogen sulfide that must be present in the flask initially if equilibrium is to be established at 25°C?

The data below refer to the following reaction: 2NO(g)+ Br₂(g) 2NOBr(g) Find the concentration of NOBr when the system reaches equilibrium.

K_c for the reaction CO₂(g)+ H₂(g) H₂O(g)+ CO(g)is 1.6 at about 990ºC.Calculate the number of moles of carbon dioxide in the final equilibrium system obtained by initially adding 1.00 mol of H₂, 2.00 mol of CO₂, 0.750 mol of H₂O, and 1.00 mol of CO to a 5.00 L reactor at 990ºC.

Sodium carbonate, Na₂CO₃(s) , can be prepared by heating sodium bicarbonate, NaHCO₃(s) . 2NaHCO₃(s) Na₂CO₃(s) + CO₂(g) + H₂O(g) K_p = 0.23 at 100ºC If a sample of NaHCO₃ is placed in an evacuated flask and allowed to achieve equilibrium at 100ºC, what will the total gas pressure be?

Consider the following equilibrium, 4NH₃(g)+ 3O₂(g) 2N₂(g)+ 6H₂O(g)+ 1531 kJ State whether the concentrations of the reactants would increase, decrease, or remain constant after ammonia was added to the system.

The equilibrium between carbon dioxide gas and carbonic acid is very important in biology and environmental science. CO₂(aq)+ H₂O(l) H₂CO₃(aq) Based on the equilibrium constant reported for this reaction (K_c = 1.70 * 10^-3), there will be more carbon dioxide in solution than carbonic acid.

A quantity of liquid methanol, CH₃OH, is introduced into a rigid 3.00-L vessel, the vessel is sealed, and the temperature is raised to 500K. At this temperature, the methanol vaporizes and decomposes according to the reaction CH₃OH(g) CO(g) + 2 H₂(g) , K_c= 6.90*10^-2. If the concentration of H₂ in the equilibrium mixture is 0.426M, what mass of methanol was initially introduced into the vessel?

For the reaction 2NOCl(g) 2NO(g) + Cl₂(g) , K_c = 8.0 at a certain temperature.What concentration of NOCl must be put into an empty 4.00 L reaction vessel in order that the equilibrium concentration of NOCl be 1.00 M?

At 700 K, the reaction 2SO₂(g) + O₂(g) 2SO₃(g) has the equilibrium constant K_c = 4.3 * 10⁶ , and the following concentrations are present: [SO₂] = 0.10 M; [SO₃] = 10.M; [O₂] = 0.10 M. Is the mixture at equilibrium? If not at equilibrium, in which direction (as the equation is written) , left to right or right to left, will the reaction proceed to reach equilibrium?

At 700 K, the reaction 2SO₂(g) + O₂(g) 2SO₃(g) has the equilibrium constant K_c = 4.3 * 10⁶, and the following concentrations are present: [SO₂] = 0.010 M; [SO₃] = 10.M; [O₂] = 0.010 M. Is the mixture at equilibrium? If not at equilibrium, in which direction (as the equation is written) , left to right or right to left, will the reaction proceed to reach equilibrium?

Equilibrium is established for the reaction 2X(s) + Y(g) 2Z(g) at 500K, K_c = 100.Determine the concentration of Z in equilibrium with 0.2 mol X and 0.50 M Y at 500K.