Kc = 5.6 1012 at 500 K for the dissociation of iodine molecules to iodine atoms. I2(g) 2 I(g) A mixture has [I2] = 0.020 mol/Land [I] = 2.0 108 mol/L. Is the reaction at equilibrium (at 500 K)? If not, which way must the reaction proceed to reach equilibrium?

Kc for the decomposition of ammonium hydrogen sulfide is 1.8 104 at 25 C. NH4HS(s) NH3(g) + H2S(g) (a) When the pure salt decomposes in a flask, what are the equilibrium concentrations of NH3 and H2S? (b) If NH4HS is placed in a flask already containing 0.020 mol/L of NH3 and then the system is allowed to come to equilibrium, what are the equilibrium concentrations of NH3 and H2S?

Consider the system 4 NH3(g) + 3 O2(g) ⇌ 2 N2(g) + 6 H20(ℓ) ΔrH° = −1530.4 kJ/mol How will the amount of ammonia at equilibrium be affected by removing O2(g) without changing the total gas volume? adding N2(g) without changing the total gas volume? adding water without changing the total gas volume? expanding the container? increasing the temperature? Which of these changes (i to v) increases the value of K? Which decreases it?

The equilibrium constant Kc for the synthesis of methanol, CH3OH. CO(g)+2H2(g)CH3OH(g) is 4.3 at 250C and 1.8 at 275C. Is this reaction endothermic or exothermic?

. Consider an equilibrium mixture consisting of H2O(g), CO(g). H2(g), and CO2(g) reacting in a closed vessel according to the equation H2O(g)+CO(g)H2(g)+CO2(g)a. You add more H2O to the flask. How does the new equilibrium concentration of each chemical compare to its origin al equilibrium concentration after equilibrium is re-established? Justify your answer. b. You add more H2to the flask. How does the concentration of each chemical compare to its original concentration after equilibrium is re-established? Justify your answer.

A mixture of SO2, O2, and SO3 at 1000 K contains the gases at the following concentrations: [SO2] = 5.0 103 mol/L, [O2] = 1.9 103 mol/L, and [SO3] = 6.9 103 mol/L. Is the reaction at equilibrium? If not, which way will the reaction proceed to reach equilibrium? 2 SO2(g) + O2(g) 2 SO3(g) Kc = 279

Nitrosyl chloride, NOC1, decomposes to NO and Cl2 at high temperatures. 2 NOCl(g) ⇌ 2 NO(g) + Cl2(g) Suppose you place 2.00 mol NOC1 in a 1.00–L flask, seal it, and raise the temperature to 462 °C. When equilibrium has been established, 0.66 mol NO is present. Calculate the equilibrium constant Kc for the decomposition reaction from these data.

Because calcium carbonate is a sink for CO32- in a lake, the student in Exercise 12.39 decides to go a step further and examine the equilibrium between carbonate ion and CaCOj. The reaction is Ca2+(aq) + COj2_(aq) ** CaCO,(s) The equilibrium constant for this reaction is 2.1 X 10*. If the initial calcium ion concentration is 0.02 AI and the carbonate concentration is 0.03 AI, what are the equilibrium concentrations of the ions? A student is simulating the carbonic acid—hydrogen carbonate equilibrium in a lake: H2COj(aq) H+(aq) + HCO}‘(aq) K = 4.4 X 10"7 She starts with 0.1000 AI carbonic acid. What are the concentrations of all species at equilibrium?

For which reactions in Exercise 34 is Kp equal to K?