Chemical Equilibrium Problems

Chemical Equilibrium Exercises

• For the reversible elementary reaction $A + B \rightleftharpoons C + D$, the equilibrium concentrations at a given temperature are:

  • $[A] = 2.0 , \text{mol/L}$
  • $[B] = 3.0 , \text{mol/L}$
  • $[C] = 4.0 , \text{mol/L}$
  • $[D] = 2.0 , \text{mol/L}$.
  • Equilibrium constant $K_c$ is calculated using these values.

• For the equilibrium $2CO(g) + O_2(g) \rightleftharpoons 2CO_2(g)$ at 727 °C, $K_c = 4.2 \times 10^6$.

  • If $[CO] = 1.2 \times 10^{-3} , \text{mol/L}$ and $[CO_2] = 0.100 , \text{mol/L}$ in a sample of exhaust gases at 727 °C, the concentration of $O_2$ in the exhaust can be determined.

• In a 2-liter container, 4 moles of hydrogen and 3 moles of iodine are placed.

  • At equilibrium at temperature T, 2 moles of $HI$ are found for the reaction $H_2(g) + I_2(g) \rightleftharpoons 2HI(g)$.
  • $K_c$ can be calculated from this data.

• In a 1-liter container at 448 °C, 1 mole of hydrogen and 1 mole of iodine are mixed, establishing the equilibrium $H_2(g) + I_2(g) \rightleftharpoons 2HI(g)$.

  • Given that $K_c = 50$ under these conditions, the number of moles of each substance at equilibrium can be determined.

• In a 5-liter container, 2 moles of phosphorus pentachloride are introduced.

  • Above 200 °C, the equilibrium $PCl_5(g) \rightleftharpoons PCl_3(g) + Cl_2(g)$ is established.
  • If the degree of dissociation of $PCl_5$ is 20%, then $K_c$ can be determined.

• At 400 °C, $K_c = 0.02$ for the equilibrium $2HI(g) \rightleftharpoons H_2(g) + I_2(g)$.

  • If 10 moles of $HI$ are placed in a 10-liter container, the number of moles of $I_2$ at equilibrium can be calculated.

• The reaction for the formation of ammonia is represented by $N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)$.

  • At a certain temperature, the partial pressures at equilibrium are:
    • $P(N_2) = 2.0 , \text{atm}$
    • $P(H_2) = 3.0 , \text{atm}$
    • $P(NH_3) = 0.5 , \text{atm}$.
  • $K_p$ can be calculated using these values.

• For the equilibrium $N_2O_4(g) \rightleftharpoons 2NO_2(g)$ at 25 °C, $K_p = 0.14$.

  • If $N_2O_4$ is introduced into a container at an initial pressure of 1.0 atm, the partial pressures of $N_2O_4$ and $NO_2$ at equilibrium can be calculated.

• Consider the equilibrium $PCl_5(g) \rightleftharpoons PCl_3(g) + Cl_2(g)$ in a closed container at 250 °C.

  • The partial pressures at equilibrium are:
    • $P(PCl_5) = 0.40 , \text{atm}$
    • $P(PCl_3) = 0.20 , \text{atm}$
    • $P(Cl_2) = 0.20 , \text{atm}$.
  • $K_p$ can be calculated from these partial pressures.
  • $K_c$ can be calculated from $K_p$ using $R = 0.082 , \text{atm} \cdot \text{L} \cdot \text{mol}^{-1} \cdot \text{K}^{-1}$.

• Consider the equilibrium $CO(g) + H_2O(g) \rightleftharpoons CO_2(g) + H_2(g)$.

  • At 700 K, $K_p = 0.534$.
  • If CO and $H_2O$ are injected into a reactor, both at a pressure of 3.00 atm, the partial pressures of all gases at equilibrium can be determined.