The Equilibrium Constant
| 1. | a. | What is meant by a reversible reaction? | |
| b. | Are all chemical reactions reversible? | ||
| c. | Are all reversible reactions always at equilibrium? | ||
| d. | Does a reaction have to be reversible in order to reach equilibrium? | ||
| e. | What, exactly, is equal at equilibrium? (define equilibrium) | ||
| f. | How is equilibrium different from a steady state system? | ||
| 2. | Write the equilibrium expression for each of the following reactions. Be sure to pay attention to physical states: | ||
| a. | Br2 (g) + 5 F2 (g) ↔ 2 BrF5 (g) | ||
| b. | 4 HCl(g) + O2 (g) ↔ 2 H2O(g) + 2 Cl2 (g) | ||
| c. | 5 Fe2+(aq) + MnO4–(aq) + 8 H+(aq) ↔ 5 Fe3+(aq) + Mn2+(aq) + 4 H2O(l) | ||
| 3. | For each of the following reactions, state whether the value of the equilibrium constant favours the formation of reactants, products, or both sides equally. | ||
| a. | I2 (g) + Cl2 (g) ↔2 ICl(g) Keq = 2×106 | ||
| b. | H2 (g) + Cl2 (g) ↔ 2 HCl(g) Keq = 1.08 | ||
| c. | I2 (g) ↔ I(g) + I(g) Keq = 3.8× 10-7 | ||
| 4. | Molecular chlorine decomposes into atoms according to the reaction: Cl2 (g) ↔ 2 Cl(g) The equilibrium constant for the reaction at 25°C is 1.4 × 10-38. Would many chlorine ATOMS be present at this temperature? How do you know? |
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| 5. | Calculate Keq for each of the following. Be sure to set up the equilibrium constant expression first, before substituting in the values. Show your work! Pay attention to exponents! |
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| a. | H2 (g) + Cl2 (g) ↔ 2 HCl | [H2] = 1.0 × 10-2M [Cl2] = 1.0 × 10-2M [HCl] = 1.0 × 10-2M |
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| b. | N2 (g) + 3 H2 (g) ↔ 2 NH3 (g) | [N2] = 4.4 × 10-2M [H2] = 1.2 × 10-1M [NH3] = 3.4 × 10-3M |
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| c. | 2 CO(g) + O2 (g) ↔ 2 CO2 (g) | [CO] = 2.5 × 10-3M [O2] = 1.6 × 10-3M [CO2] = 3.2 × 10-2M |
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| d. | CH4 (g)+ H2O(g) ↔ CO(g) + 3 H2 (g) | [CH4] = 2.97 × 10-3M [H2O] = 7.94 × 10-3M [CO] = 5.45 × 10-3M [H2] = 2.1 × 10-3M |
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| 6. | For the following reaction at equilibrium at 2000°C, the concentration of N2 and O are both 5.2 M. N2 (g) + O2 (g) ↔ 2 NO2 (g) Keq = 6.2 × 10-4 Calculate the concentration of NO at equilibrium. Show your work; pay careful attention to exponents. |
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| 7. | Acetic acid, HC2H3O2, is in equilibrium with its ions: HC2H3O2 (aq) ↔ H+(aq) + C2H3O2–(aq) Keq = 1.8 × 10-5 At equilibrium, the concentration of the ions are:
Calculate the concentration of the acid, HC2H3O2. |
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