13.4 Equilibrium calculations  (Page 10/11)

Calculate the equilibrium concentrations of NO, O ₂ , and NO ₂ in a mixture at 250 °C that results from the reaction of 0.20 M NO and 0.10 M O ₂ . (Hint: K is large; assume the reaction goes to completion then comes back to equilibrium.)

$2\text{NO}(g)+{\text{O}}_2(g)\rightleftharpoons 2{\text{NO}}_2(g)K_c=2.3\times {10}^5\text{at}250\text{°C}$

Calculate the equilibrium concentrations that result when 0.25 M O ₂ and 1.0 M HCl react and come to equilibrium.

$4\text{HCl}(g)+{\text{O}}_2(g)\rightleftharpoons 2{\text{Cl}}_2(g)+2{\text{H}}_2\text{O}(g)K_c=3.1\times {10}^{13}$

One of the important reactions in the formation of smog is represented by the equation

${\text{O}}_3(g)+\text{NO}(g)\rightleftharpoons {\text{NO}}_2(g)+{\text{O}}_2(g)K_P=6.0\times {10}^{34}$

What is the pressure of O ₃ remaining after a mixture of O ₃ with a pressure of 1.2 $\times$ 10 ⁻⁸ atm and NO with a pressure of 1.2 $\times$ 10 ⁻⁸ atm comes to equilibrium? (Hint: K _P is large; assume the reaction goes to completion then comes back to equilibrium.)

Calculate the pressures of NO, Cl ₂ , and NOCl in an equilibrium mixture produced by the reaction of a starting mixture with 4.0 atm NO and 2.0 atm Cl ₂ . (Hint: K _P is small; assume the reverse reaction goes to completion then comes back to equilibrium.)

$2\text{NO}(g)+{\text{Cl}}_2(g)\rightleftharpoons 2\text{NOCl}(g)K_P=2.5\times {10}^3$

Calculate the number of grams of HI that are at equilibrium with 1.25 mol of H ₂ and 63.5 g of iodine at 448 °C.

${\text{H}}_2+{\text{I}}_2\rightleftharpoons 2\text{HI}{K}_c=50.2\text{at}448\text{°C}$

Butane exists as two isomers, n −butane and isobutane.

K _P = 2.5 at 25 °C

What is the pressure of isobutane in a container of the two isomers at equilibrium with a total pressure of 1.22 atm?

What is the minimum mass of CaCO ₃ required to establish equilibrium at a certain temperature in a 6.50-L container if the equilibrium constant ( K _c ) is 0.050 for the decomposition reaction of CaCO ₃ at that temperature?

${\text{CaCO}}_3(s)\rightleftharpoons \text{CaO}(s)+{\text{CO}}_2(g)$

The equilibrium constant ( K _c ) for this reaction is 1.60 at 990 °C:

${\text{H}}_2(g)+{\text{CO}}_2(g)\rightleftharpoons {\text{H}}_2\text{O}(g)+\text{CO}(g)$

Calculate the number of moles of each component in the final equilibrium mixture obtained from adding 1.00 mol of H ₂ , 2.00 mol of CO ₂ , 0.750 mol of H ₂ O, and 1.00 mol of CO to a 5.00-L container at 990 °C.

At 25 °C and at 1 atm, the partial pressures in an equilibrium mixture of N ₂ O ₄ and NO ₂ are ${\text{P}}_{{\text{N}}_2{\text{O}}_4}=0.70\text{atm}$ and ${\text{P}}_{{\text{NO}}_2}=0.30\text{atm.}$

(a) Predict how the pressures of NO ₂ and N ₂ O ₄ will change if the total pressure increases to 9.0 atm. Will they increase, decrease, or remain the same?

(b) Calculate the partial pressures of NO ₂ and N ₂ O ₄ when they are at equilibrium at 9.0 atm and 25 °C.

In a 3.0-L vessel, the following equilibrium partial pressures are measured: N ₂ , 190 torr; H ₂ , 317 torr; NH ₃ , 1.00 $\times$ 10 ³ torr.

${\text{N}}_2(g)+3{\text{H}}_2(g)\rightleftharpoons 2{\text{NH}}_3(g)$

(a) How will the partial pressures of H ₂ , N ₂ , and NH ₃ change if H ₂ is removed from the system? Will they increase, decrease, or remain the same?

(b) Hydrogen is removed from the vessel until the partial pressure of nitrogen, at equilibrium, is 250 torr. Calculate the partial pressures of the other substances under the new conditions.

The equilibrium constant ( K _c ) for this reaction is 5.0 at a given temperature.

$\text{CO}(g)+{\text{H}}_2\text{O}(g)\rightleftharpoons {\text{CO}}_2(g)+{\text{H}}_2(g)$

(a) On analysis, an equilibrium mixture of the substances present at the given temperature was found to contain 0.20 mol of CO, 0.30 mol of water vapor, and 0.90 mol of H ₂ in a liter. How many moles of CO ₂ were there in the equilibrium mixture?

(b) Maintaining the same temperature, additional H ₂ was added to the system, and some water vapor was removed by drying. A new equilibrium mixture was thereby established containing 0.40 mol of CO, 0.30 mol of water vapor, and 1.2 mol of H ₂ in a liter. How many moles of CO ₂ were in the new equilibrium mixture? Compare this with the quantity in part (a), and discuss whether the second value is reasonable. Explain how it is possible for the water vapor concentration to be the same in the two equilibrium solutions even though some vapor was removed before the second equilibrium was established.