Chem - 17

At 25°C, the equilibrium constant Kc for the reaction 2A(aq) B(aq) + C(aq) is 65. If 2.50 mol of A is added to enough water to prepare 1.00 L of solution, what will the equilibrium concentration of A be?

.14

The equilibrium constant Kc for the reaction A(g) + B(g) C(g) is 0.76 at 150°C. If 0.800 mol of A is added to 0.600 mol of B in a 1.00-L container at 150°C, what will be the equilibrium concentration of C?

.19

At a certain temperature the reaction CO2(g) + H2(g) CO(g) + H2O(g)2 has Kc = 2.50. If 2.00 mol of carbon dioxide and 1.5 mol of hydrogen are placed in a 5.00 L vessel and equilibrium is established, what will be the concentration of carbon monoxide?

.209

Ammonium iodide dissociates reversibly to ammonia and hydrogen iodide. NH4I(s) NH3(g) + HI(g) At 400°C, Kp = 0.215. Calculate the partial pressure of ammonia at equilibrium when a sufficient quantity of ammonium iodide is heated to 400°C.

.464

At 25°C, the equilibrium constant Kc for the reaction 2A(g) B(g) + C(g) is 0.035. A mixture of 8.00 moles of B and 12.00 moles of C in a 20.0 L container is allowed to come to equilibrium. What is the equilibrium concentration of A?

.678

At 850°C, the equilibrium constant Kp for the reaction C(s) + CO2(g) 2CO(g) has a value of 10.7. If the total pressure in the system at equilibrium is 1.000 atm, what is the partial pressure of carbon monoxide?

.921

10.0 mL of a 0.100 mol L-1 solution of a metal ion M2+ is mixed with 10.0 mL of a 0.100 mol L-1 solution of a substance L. The following equilibrium is established: M2+(aq) + 2L(aq) ML22+(aq) At equilibrium the concentration of L is found to be 0.0100 mol L-1. What is the equilibrium concentration of ML22+, in mol L

0.0200 mol L-1

At high temperatures, carbon reacts with O2 to produce CO as follows: C(s) + O2(g) 2CO(g). When 0.350 mol of O2 and excess carbon were placed in a 5.00-L container and heated, the equilibrium concentration of CO was found to be 0.060 M. What is the equilibrium constant, Kc, for this reaction?

0.090

The equilibrium constant Kc for the reaction PCl3(g) + Cl2(g) PCl5(g) is 49 at 230°C. If 0.70 mol of PCl3 is added to 0.70 mol of Cl2 in a 1.00-L reaction vessel at 230°C, what is the concentration of PCl3 when equilibrium has been established?

0.11 M

SO2 reacts with O2 to produce SO3. If 86.0 g of SO2 is placed in a reaction vessel along with excess oxygen gas, how many moles of SO2 remain when 50.0 g of SO3 have been formed?

0.72 mol

N2(g) + O2(g) 2NO(g) Kc = 4.8 × 10-31 2NOBr(g) 2NO(g) + Br2(g) Kc = 0.50 Given the above equilibrium constant data at 25°C, what is the value of Kc at this temperature for the reaction

1.0 × 1030

H+(aq) + OH-(aq) H2O(l) In pure water at 25°C, the concentration of H+ ions is 1.00 × 10-7 mol/L. Calculate the value of the equilibrium constant for the reaction as written above.

1.00 × 1014

Hydrogen sulfide will react with water as shown in the following reactions. H2S(g) + H2O(l) H3O+(aq) + HS-(aq) K1 = 1.0 × 10-7 HS-(aq) + H2O(l) H3O+(aq) + S2-(aq) K2 = ? H2S(g) + 2H2O(l) 2H3O+(aq) + S2-(aq) K3 = 1.3 × 10-20 What is the value of K2?

1.3 × 10-13

The equilibrium constant for the reaction of bromine with chlorine to form bromine monochloride is 58.0 at a certain temperature. Br2(g) + Cl2(g) 2BrCl(g) What is the equilibrium constant for the following reaction? BrCl(g) ½Br2(g) + ½Cl2(g)

1.31 × 10-1

The equilibrium constant for reaction (1) below is 276. Under the same conditions, what is the equilibrium constant of reaction (2)? (1) ½X2(g) + ½Y2(g) XY(g) (2) 2XY(g) X2(g) + Y2(g)

1.31 × 10-5

The equilibrium constant Kc is known to be 0.141. If the initial concentration of chlorine is 0.0300 M and of bromine monochloride is 0.0200 M, what is the equilibrium concentration of bromine?

1.35 × 10-3 M

The equilibrium constant, Kp, has a value of 6.5 × 10-4 at 308 K for the reaction of nitrogen monoxide with chlorine. 2NO(g) + Cl2(g) 2NOCl(g) What is the value of Kc?

1.6 × 10-2

Nitrogen dioxide decomposes according to the reaction 2NO2(g) 2NO(g) + O2(g) where Kp = 4.48 × 10-13 at 25°C. What is the value for Kc?

1.83 × 10-14

Nitric oxide and bromine were allowed to react in a sealed container. When equilibrium was reached PNO = 0.526 atm, = 1.59 atm, and PNOBr = 7.68 atm. Calculate Kp for the reaction. 2NO(g) + Br2(g) 2NOBr(g)

134

Hydrogen sulfide can be formed in the following reaction: H2(g) + ½S2(g) H2S(g) ΔH°rxn = -92 kJ The equilibrium constant Kp = 106 at 1023 K. Estimate the value of Kp at 1218 K.

18.8

Hydrogen iodide, HI, is formed in an equilibrium reaction when gaseous hydrogen and iodine gas are heated together. If 20.0 g of hydrogen and 20.0 g of iodine are heated, forming 10.0 g of hydrogen iodide, what mass of hydrogen remains unreacted?

19.9 g hydrogen remains

Consider the reactions of cadmium with the thiosulfate anion. Cd2+(aq) + S2O32-(aq) Cd(S2O3)(aq) K1 = 8.3 × 103 Cd(S2O3)(aq) + S2O32-(aq) Cd(S2O3)22-(aq) K2 = 2.5 × 102 What is the value for the equilibrium constant for the following reaction? Cd2+(aq) + 2S2O32-(aq) Cd(S2O3)22-(aq)

2.1 × 106

At 500°C the equilibrium constant, Kp, is 4.00 × 10-4 for the equilibrium: 2HCN(g) H2(g) + C2N2(g) What is Kp for the following reaction? H2(g) + C2N2(g) 2HCN(g) A. 2.00 × 10-4 B. -4.00 × 10-4 C. 1.25 × 103

2.50 × 103

The equilibrium constant, Kc, for the decomposition of COBr2 COBr2(g) CO(g) + Br2(g) is 0.190. What is Kc for the following reaction? 2CO(g) + 2Br2(g) 2COBr2(g)

27.7

A mixture of 0.600 mol of bromine and 1.600 mol of iodine is placed into a rigid 1.000-L container at 350°C. Br2(g) + I2(g) 2IBr(g) When the mixture has come to equilibrium, the concentration of iodine monobromide is 1.190 M. What is the equilibrium constant for this reaction at 350°C?

282

Stearic acid, nature's most common fatty acid, dimerizes when dissolved in hexane: 2C17H35COOH (C17H35COOH)2 ΔH°rxn = -172 kJ The equilibrium constant for this reaction at 28°C is 2900. Estimate the equilibrium constant at 38°C.

3.2 × 102

Compounds A, B, and C react according to the following equation. 3A(g) + 2B(g) 2C(g) At 100°C a mixture of these gases at equilibrium showed that [A] = 0.855 M, [B] = 1.23 M, and [C] = 1.75 M. What is the value of Kc for this reaction?

3.24

Consider the equilibrium reaction shown below. B2(g) 2B(g) If the rate constants are: kfwd = 7.00 × 10-5s-1 and krev = 2.00 × 10-5 L mol-1 s-1, what is the value of Kc under these conditions?

3.50

The reaction of nitrogen with oxygen to form nitrogen monoxide can be represented by the following equation. N2(g) + O2(g) 2NO(g) At 2000°C, the equilibrium constant, Kc, has a value of 4.10 × 10-4. What is the value of Kp?

4.10 × 10-4

An equilibrium is established in which both the forward (fwd) and the reverse (rev) reactions are elementary. If the equilibrium constant Kc = 1.6 × 10-2 and the rate constant kfwd = 8.0 × 10-7 s-1 what is the value of krev?

5.0 × 10-5 s-1

A mixture of 0.500 mole of carbon monoxide and 0.400 mole of bromine was placed into a rigid 1.00-L container and the system was allowed to come to equilibrium. The equilibrium concentration of COBr2 was 0.233 M. What is the value of Kc for this reaction? CO(g) + Br2(g) COBr2(g)

5.23

H2SO3(aq) HSO3(aq) + H+(aq) Kc = 1.4 × 10-2 H2SO3(aq) SO32-(aq) + 2H+(aq) Kc = 9.1 × 10-10 Given the above equilibrium constant data at 25°C, what is the value of Kc at this temperature for the reaction

6.5 ×10-8

Consider the reversible reaction: 2NO2(g) N2O4(g) If the concentrations of both NO2 and N2O4 are 0.016 mol L-1, what is the value of c?

63

Nitric oxide is formed in automobile exhaust when nitrogen and oxygen in air react at high temperatures. N2(g) + O2(g) 2NO(g) The equilibrium constant Kp for the reaction is 0.0025 at 2127°C. If a container is charged with 8.00 atm of nitrogen and 5.00 atm of oxygen and the mixture is allowed to reach equilibrium, what will be the equilibrium partial pressure of nitrogen?

7.8 atm

The reaction system CS2(g) + 4H2(g) CH4(g) + 2H2S(g) is at equilibrium. Which of the following statements describes the behavior of the system if the partial pressure of carbon disulfide is reduced?

As equilibrium is reestablished, the partial pressure of carbon disulfide increases.

The reaction system CS2(g) + 4H2(g) CH4(g) + 2H2S(g) is at equilibrium. Which of the following statements describes the behavior of the system if the partial pressure of hydrogen is doubled?

As equilibrium is reestablished, the partial pressure of hydrogen decreases.

Carbon monoxide and chlorine combine in an equilibrium reaction to produce the highly toxic product, phosgene (COCl2) CO(g) + Cl2(g) COCl2(g) If the equilibrium constant for this reaction is Kc = 248, predict, if possible, what will happen when the reactants and product are combined with the concentrations shown. [CO] = [Cl2] = 0.0200 M; [COCl2] = 0.0992 M

C. The reaction is at equilibrium, and no change in concentrations will occur.

A container was charged with hydrogen, nitrogen, and ammonia gases at 120°C and the system was allowed to reach equilibrium. What will happen if the volume of the container is increased at constant temperature?

Hydrogen and nitrogen will be produced at the expense of ammonia.

About half of the sodium carbonate produced is used in making glass products because it lowers the melting point of sand, the major component of glass. When sodium carbonate is added to water it hydrolyses according to the following reactions. CO32-(aq) + H2O(l) HCO3-(aq) + OH-(aq) K1 HCO3(aq) + H2O(l) H2CO3(aq) + OH-(aq) K2 These can be combined to yield CO32-(aq) + 2H2O(l) H2CO3(aq) + 2OH-(aq) K3 What is the value of K3?

K1 × K2

Consider the following two equilibria and their respective equilibrium constants: (1) NO(g) + ½O2(g) NO2(g) (2) 2NO2(g) 2NO(g) + O2(g) Which one of the following is the correct relationship between the equilibrium constants K1 and K2?

K2 = (1/K1)2

Consider the equilibrium reaction: H2(g) + Br2(g) 2HBr(g) Which of the following correctly describes the relationship between Kc and Kp for the reaction?

Kp = Kc

Consider the equilibrium reaction: N2O4(g) 2NO2(g) Which of the following correctly describes the relationship between Kc and Kp for the reaction?

Kp = RT × Kc

The equilibrium constant, Kp, for the reaction CO(g) + H2O(g) CO2(g) + H2(g) at 986°C is 0.63. A rigid cylinder at that temperature contains 1.2 atm of carbon monoxide, 0.20 atm of water vapor, 0.30 atm of carbon dioxide, and 0.27 atm of hydrogen. Is the system at equilibrium?

No, the forward reaction must proceed to establish equilibrium.

The equilibrium constant, Kp, for the reaction H2(g) + I2(g) 2HI(g) is 55.2 at 425°C. A rigid cylinder at that temperature contains 0.127 atm of hydrogen, 0.134 atm of iodine, and 1.055 atm of hydrogen iodide. Is the system at equilibrium?

No, the reverse reaction must proceed to establish equilibrium.

The following reaction is at equilibrium in a closed container. CuSO4.5H2O(s) CuSO4(s) + 5H2O(g) Which, if any, of the following actions will lead to an increase in the pressure of H2O present at equilibrium?

None of these choices are correct.

The reaction system POCl3(g) POCl(g) + Cl2(g) is at equilibrium. Which of the following statements describes the behavior of the system if the partial pressure of chlorine is reduced by 50%?

POCl3 will be consumed as equilibrium is established

The reaction quotient for a gas phase reaction has a value of 2000. If the number of moles of reactants in the reaction equation is equal to that of the products, which of the following statements is definitely TRUE?

The concentrations of the products are generally larger than the concentrations of the reactants.

A chemical reaction has an equilibrium constant of 2 × 106. If this reaction is at equilibrium, select the one correct conclusion that can be made about the reaction.

The forward and reverse reaction rates are equal.

Magnesium hydroxide is used in several antacid formulations. When it is added to water it dissociates into magnesium and hydroxide ions. Mg(OH)2(s) Mg2+(aq) + 2OH-(aq) The equilibrium constant at 25°C is 8.9 × 10-12. One hundred grams of magnesium hydroxide is added to 1.00 L of water and equilibrium is established. What happens to the solution if another 10 grams of Mg(OH)2 are now added to the mixture?

The hydroxide ion concentration will be unchanged.

The reaction of nitric oxide to form dinitrogen oxide and nitrogen dioxide is exothermic. 3NO(g) N2O(g) + NO2(g) + heat What effect will be seen if the temperature of the system at equilibrium is raised by 25°C?

The partial pressure of NO will increase.

Magnesium carbonate dissociates to magnesium oxide and carbon dioxide at elevated temperatures. MgCO3(s) MgO(s) + CO2(g) A reaction vessel contains these compounds in equilibrium at 300°C. What will happen if the volume of the container is reduced by 25% at 300°C?

The partial pressure of carbon dioxide at equilibrium will be unchanged.

Sodium hydrogen carbonate decomposes above 110°C to form sodium carbonate, water, and carbon dioxide. 2NaHCO3(s) Na2CO3(s) + H2O(g) + CO2(g) One thousand grams of sodium hydrogen carbonate are added to a reaction vessel, the temperature is increased to 200°C, and the system comes to equilibrium. What happens in this system if another 50 g of sodium carbonate are now added?

The partial pressure of carbon dioxide will be unchanged.

Methanol can be synthesized by combining carbon monoxide and hydrogen. CO(g) + 2H2(g) CH3OH(g) ΔH°rxn = -90.7 kJ A reaction vessel contains these compounds at equilibrium. What effect will be seen when equilibrium is re-established after decreasing the temperature by 45°C?

The partial pressure of carbon monoxide will decrease.

Methanol can be synthesized by combining carbon monoxide and hydrogen. CO(g) + 2H2(g) CH3OH(g) A reaction vessel contains the three gases at equilibrium with a total pressure of 1.00 atm. What will happen to the partial pressure of hydrogen if enough argon is added to raise the total pressure to 1.4 atm?

The partial pressure of hydrogen will be unchanged.

Hydrogen bromide will dissociate into hydrogen and bromine gases. 2HBr(g) H2(g) + Br2(g) ΔH°rxn = 68 kJ What effect will a temperature increase of 50°C have on this system at equilibrium?

The partial pressure of hydrogen will increase.

The reaction quotient, c, for a reaction has a value of 75 while the equilibrium constant, Kc, has a value of 195. Which of the following statements is accurate?

The reaction must proceed to the right to establish equilibrium.

Carbon monoxide and chlorine combine in an equilibrium reaction to produce the highly toxic product, phosgene (COCl2) CO(g) + Cl2(g) COCl2(g)[CO] = [Cl2] = 0.010 M; [COCl2] = 0.070 M k=248

The reaction will proceed to the left.

The reaction system POCl3(g) POCl(g) + Cl2(g) is at equilibrium. Which of the following statements describes the behavior of the system if POCl is added to the container?

The reverse reaction will proceed to establish equilibrium.

At 450°C, tert-butyl alcohol decomposes into water and isobutene. (CH3)3COH(g) (CH3)2CCH2(g) + H2O(g) A reaction vessel contains these compounds at equilibrium. What will happen if the volume of the container is reduced by 50%at constant temperature?

The reverse reaction will proceed to reestablish equilibrium.

The following reaction is at equilibrium at one atmosphere, in a closed container. NaOH(s) + CO2(g) NaHCO3(s) Which, if any, of the following actions will decrease the total amount of CO2 gas present at equilibrium?

decreasing the volume of the container

In order to write the correct mass-action expression for a reaction one must

have a properly balanced chemical equation.

Nitrogen dioxide can dissociate to nitric oxide and oxygen. 2NO2(g) 2NO(g) + O2(g) ΔH°rxn = +114 kJ

high temperature, low pressure

The two equilibrium constants for the same reaction, Kc and Kp, will always equal one another when

in the reaction equation, the number of moles of gaseous products equals the number of moles of gaseous reactants.

Ethane can be formed by reacting acetylene with hydrogen. C2H2(g) + 2H2(g) C2H6(g) ΔH°rxn = -311 kJ Under which reaction conditions would you expect to have the greatest equilibrium yield of ethane?

low temperature, high pressure

The following reaction is at equilibrium at a pressure of 1 atm, in a closed container. NaOH(s) + CO2(g) NaHCO3(s) ΔH°rxn < 0 Which, if any, of the following actions will decrease the concentration of CO2 gas present at equilibrium?

lowering the temperature

The following reaction is at equilibrium in a sealed container. N2(g) + 3H2(g) 2NH3(g) ΔH°rxn < 0 Which, if any, of the following actions will increase the value of the equilibrium constant, Kc?

lowering the temperature

When a chemical system is at equilibrium,

the concentrations of the reactants and products have reached constant values