_{c}or K

_{p }if applicable, for the following reversible reactions at equilibrium:

(a) PCl

(b) HF (aq) + H

(c) 2 NO (g) + O

(d) N

(e) NH

(f) CaCO

(g) H

_{3}(g) + Cl_{2}(g) ↔ PCl_{5}(g)(b) HF (aq) + H

_{2}O (l) ↔ H_{3}O^{+ }(aq) + F^{- }(aq)(c) 2 NO (g) + O

_{2 }(g) ↔ 2 NO_{2 }(g)(d) N

_{2}(g) + 3H_{2}(g) ↔ 2 NH_{3}(g)(e) NH

_{4}Cl (s) ↔ NH_{3}(g) + HCI (g)(f) CaCO

_{3}(s) ↔ CaO (s) + CO_{2}(g)(g) H

_{2}O (l) + SO_{3 }(g) ↔ H_{2}SO_{4 }(aq)2. Calculate K

_{p }for the following reactions:

_{2}O (g) ↔ CO

_{2}(g) + H

_{2}(g), K

_{c}= 4.05 at 500

^{o}C

(b) 2CO (g) + O

_{2}(g) ↔ 2CO

_{2}(g), K

_{c}= 2.24 x 10

^{22}at 1273

^{o}C

3. Calculate K

_{c }for the following reactions:

(a) 2 NO

_{2}(g) ↔ N

_{2}O

_{4}(g), K

_{p}

*=*6.5 x 10

^{-2 }at 100

^{o}C

(b) 2 SO

_{3 }(g) ↔ 2 SO

_{2}(g) + O

_{2}(g), K

_{p}

*=*1.8 x 10

^{-5}at 350

^{o}C

N

_{2}(g) + 3 H

_{2}(g) ↔ 2 NH

_{3}(g) K

_{c}= 2.4x10

^{-3}at 1000 K

Calculate the K

_{c}for the following balanced equations at the same temperature.

(a) 1/3 N

_{2}(g) + H

_{2}(g) ↔ 2/3NH

_{3}(g)

(b) NH

_{3}(g) ↔ ½N

_{2}(g) + 3/2H

_{2}(g)

5. For the following reaction at 60

^{o}C:

_{2}S (g) + I

_{2}(s) ↔ 2 HI (g) + S (s)

the partial pressure of P

_{HI }= 3.65x10

^{-3}atm and P

_{H2S}= 0.996 atm at equilibrium. Calculate K

_{p}.

6. An equal amount of hydrogen and iodine are injected into a 1.50 L flask at a fixed temperature.

H

_{2 }(g) + I

_{2 }(g) ↔ 2 HI (g)

At equilibrium, it is found that the flask contains 1.80 mol of H

_{2}, 1.80 mol of I

_{2}and 0.520 mol of HI. Calculate K

_{c}.

7. 0.200 mol of hydrogen halide is injected into a 2.00 L flask at a fixed temperature.

2 HI (g) ↔ H

If [HI] = 0.078 M at equilibrium, calculate K_{2 }(g) + I_{2 }(g)_{c}.

8. At 25°C, 0.0560 mol of O

_{2}and 0.020 mol N

_{2}O are placed in a 1.00 L vessel and allowed to react according to the following equation:

2 N

_{2}O (g) + 3 O

_{2 }(g) ↔ 4 NO

_{2 }(g)

When the system reached equilibrium, the concentration of NO

_{2}was found to be 0.020 mol L

^{-1}.

(a) Calculate the concentration of N

_{2}O and O

_{2}at equilibrium.

(b) Calculate the equilibrium constant, K

_{c}for the reaction.

9. At 25°C, K

_{p }= 7.13 for the following reaction:

2 NO

_{2 }(g) ↔ N

_{2}O

_{4 }(g)

If the partial pressure of NO

_{2}in a container is 0.15 atm at equilibrium, calculate the equilibrium partial pressure of N_{2}O_{4}in the mixture.10. The equilibrium constant K

_{p}for the following reaction is 158 at 1000K:

2 NO

_{2}(g) ↔ 2 NO (g) + O

_{2}(g)

Calculate the P

_{O2}at equilibrium if P_{NO2}= 0.400 atm and P_{NO}= 0.270 atm at equilibrium.11. At 440°C, the equilibrium constant K

_{c }= 49.5 for the following reaction:

_{2 }(g) + I

_{2 }(g) ↔ 2 HI (g)

If 0.200 mol of H

_{2}and 0.20 mol of I

_{2}are placed into a 10.0 L vessel and allowed to react at this temperature, calculate the concentration of each substance at equilibrium.

12. The equilibrium constant, K

_{c}= 0.00465 for the following reaction at 25

^{o}C:

N

_{2}O

_{4 }(g) ↔ 2 NO

_{2}(g)

If 0.67 M of N

_{2}O

_{4}is injected into a vessel at the beginning of the reaction, calculate the equilibrium concentration of each substance at the same temperature.

13. 500 mol of ICl was placed in a 5.00 L flask and allowed to decompose at a high temperature:

2 ICl (g) ↔ I

_{2 }(g) + Cl_{2}(g) K_{c}= 0.110Calculate the concentration of I

_{2}, Cl_{2}and ICl at equilibrium._{2}and 2.000 mol of I

_{2}at 448

^{o}C.

H2 (g) + I2 (g) ↔ 2 HI (g) Kc = 50.5 at 448

^{o}C

Calculate the partial pressure of H

_{2}, I

_{2}and HI at equilibrium.

15. At 600 K, K

_{c}for the following reaction is 1.7 x 10

^{8},

2 SO

_{2}(g) + O

_{2}(g) ↔ 2 SO

_{3}(g)

(a) Calculate the partial pressure of SO

_{2}(g) at equilibrium, if P

_{SO3}= 300 atm and P

_{O2}= 100 atm at equilibrium.

(b) If a mixture of 0.0040 mol of SO

_{2 }(g) and 0.0028 mol of O

_{2}(g) is placed in a 1.0 L container and the temperature is increased to 1000 K, 0.0020 mol of SO

_{3}(g) is present at equilibrium. Calculate K

_{c }and P

_{SO2}at equilibrium for this reaction at 1000 K.

16. 0.4 mol of phosgene, COCl

_{2}in a 2.0 L vessel decomposes into CO and Cl_{2}at 200^{o}C. At equilibrium, it is found that 15% of phosgene had been decomposed. Determine the equilibrium constant, K_{p}for this reaction at 200^{o}C.17. At 250

^{o}C and 1 atm, the equilibrium constant, K_{p}for the dissociation of N_{2}O_{4}to form NO_{2}is 9.18 x 10^{-2}. Calculate the degree of dissociation of N_{2}O_{4}under these conditions.18. At 375°C, the initial concentration of N

_{2}, H_{2 }and NH_{3}are 0.0711 M, 9.17 x 10^{-3}M and 1.83 x 10^{-4 }M respectively. 3 H

_{2}(g) + N_{2}(g) ↔ 2 NH_{3}(g) If the equilibrium constant, K

_{c}for the reaction is 1.2 at this temperature, decide whether the system is at equilibrium. If it is not, predict in which direction the reaction will proceed to reach equilibrium.19. At 425

^{o}C, K_{p}= 4.18 x 10^{-9}for the reaction 2 HBr (g) ↔ H

_{2}(g) + Br_{2}(g) In one experiment, 0.20 atm of HBr (g), 0.010 atm of H

_{2}(g), and 0.010 atm of Br_{2 }(g) are introduced into a container. Is the system at equilibrium? If not, in which direction will it proceed to reach equilibrium?20. The water–gas shift reaction plays a central role in the chemical methods for obtaining cleaner fuels from coal:

CO (g) + H

_{2}O (g) ↔ CO_{2}(g) + H_{2}(g) In a given temperature, K

_{p}= 2.7. If 0.13 mol of CO, 0.56 mol of H_{2}O, 0.62 mol of CO_{2}, and 0.43 mol of H_{2}are introduced into a 2.0 L flask, in which direction must the reaction proceed to reach equilibrium?Answer

2. (a) 4.05

(b) 1.77 x 10

^{20}3. (a) 1.99

(b) 3.52 x 10

^{-7}4. (a) 0.134

(b) 20.41

5. 1.34 x 10

^{-5}6. 0.0836

7. 0.02

8. (a) [N

_{2}O] = 0.01 M [O

_{2}] = 0.041 M (b) 23.2

9. 0.16 atm

10. 347 atm

11. [H

_{2}] = [I_{2}] = 0.0044 M [HI] = 0.0312 M

12. [N

_{2}O_{4}] = 0.643 M [NO

_{2}] = 0.055 M13. [I

_{2}] = [Cl_{2}] = 0.02 M [ICl] = 0.06 M

14. H

_{2}= 3.85 atm I

_{2}= 63.01 atm HI = 110.64 atm

15. (a) 0.016 atm

(b) K

_{c}= 555.6 0.164 atm

16. 0.20

17. 0.15

18. →

19. ←

20. ←

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