Chapter 8: Unit 5. Magnitude of Equilibrium Constant
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Magnitude of Equilibrium Constant
The magnitude of the equilibrium constant Keq can predict the direction of the chemical equilibrium. Three cases can be distinguished:
1. Keq >> 1
In this case, more products amount is present than the reactant and the reaction favors the products. The reaction is said to be complete.
2. Keq << 1
In this case, more reactants amount is present than the products and the reaction favors the reactants. The reaction is barely progressed.
3. Keq is close to 1 (Keq ~ 1)
In this case, the amount of products and the amount of reactants are close to each other and the reaction is said to be moderate.
A You Tube video illustrates the equilibrium constant calculation:
http://www5.csudh.edu/oliver/chemdata/data-kc.htm
| REACTION | Kc or Kp | T |
| ANTIMONY COMPOUNDS | ||
| SbC5(g)ß à SbC3(g) + C2(g) | Kp = 2.5 x 10-2 | 248C |
| CARBON COMPOUNDS | ||
| CO(g) + 2H2(g)ß à CH3OH(g) | Kc = 14.5(c) | 500 K |
| CaCO3(s) ß à CaO(s) + CO2(g) | K=1.9 x 10-23 | 298 K |
| K=1.0 | 1200 K | |
| C(s) + H2O(g)ß à CO(g) + H2(g) | K=1.6 x 10-21 | 298 K |
| K=10.0 | 1100 K | |
| C(graphite) + CO2(g)ß à 2CO(g) | Kc = 0.64 | 1200 K |
| CO2(g) + H2(g) ß à CO(g) + H2O(g) | Kc = 1.4 | 1200 K |
| C(graphite) + 1/2 O2(g)ß à CO(g) | Kc = 1 x 103 | 1200 K |
| CO(g) + C2(g) ß à COC2(g) | Kc = 1.2 x 103 | 668 K |
| CO(g) + H2O(g)ß à CO2(g) + H2(g) | Kc = 23.2 | ? |
| 2CH4(g) ß à C2H2(g) + 3H2(g) | Kc = 0.154 | 2000 K |
| 2COF2(g) ß à CO2(g) + CF4(g) | Kc= 2.00 | 1000C |
| COC2(g) ß à CO(g) + C2(g) | Kp = 4.44 x 10-2 | 395C |
| IODINE COMPOUNDS | ||
| H2(g) + I2(g)ß à 2HI(g) | Kc = 50.2 | 445C |
| H2(g) + I2(g) ß à 2HI(g) | Kp = 6.9 x 101 | 340C |
| I2(g) ß à 2I(g) | Kc = 1.1 x 10-2 | 1200C |
| NITROGEN COMPOUNDS |
| N2(g) + 1/2 O2(g)ß à N2O(g) | Kc= 2.4 x 10-18 | |
| N2(g) + O2(g) ß à 2NO(g) | Kc = 4.1 x 10-31 | |
| N2(g) + O2(g)ß à 2NO(g) | Kc = Kp = 1.7 x 10-3 | 2300K |
| N2O(g) + 1/2 O2(g)ß à 2 NO(g) | Kc = 1.7 x 10-13 | |
| 2NO(g) + Br2(g) ß à 2NOBr(g) | Kc = 1.32 x 10-2 | 1000 K |
| N2O4(g) ß à 2NO2(g) | Kc = 4.61 x 10-3 | 25C |
| HCONH2(g)ß à NH3(g) + CO(g) | Kc = 4.84 | 400 K |
| N2(g) + 3H2(g)ß à 2NH3(g) | Kc= 152 | 500 K |
| N2(g) + 3H2(g) ß à 2NH3(g) | Kp= 4.34 x 10-3 | 300C |
| Kp = 1.45 x 10-5 | 500C | |
| Kp = 2.25 x 10-6 | 600C | |
| OXYGEN COMPOUNDS | ||
| 2H2(g) + O2(g) ß à 2H2O(g) | 3.2 x 1081 | 25C |
| PHOSPHORUS COMPOUNDS | ||
| PC5(g)ß à PC3(g) + C2(g) | Kc = 3.8 x 10-2 | 250C |
| SULFUR COMPOUNDS | ||
| 1/8 S8(s) + O2(g)ß à SO2(g) | K=4.2 x 1052 | 25C |
| 2 SO2(g) + O2(g) ß à 2 SO3(g) | Kc= 280 | 1000 K |
| 2 H2S(g) ß à 2 H2(g) + S2(g) | Kp = 0.012 | 1065C |
| 2 H2(g) + O2(g) ß à 2 H2O() | K=1.4 x 1083 | 298 K |
| NH4HS(s) ß à NH3(g) + H2S(g) | Kp = 0.108 | 25C |
| 2H2S(g) ß à 2H2(g) + S2(g) | Kc = 1.0 x 10-6 | 1000 K |
| SO2C2(g) ß à SO2(g) + C2(g) | Kp = 2.9 x 10-2 |
Quizzes