chemical equilibrium examples

🧪 Quick Study Guide

• ⚖️ Chemical equilibrium is the state where the rate of the forward reaction equals the rate of the reverse reaction.
• ➡️ This means the concentrations of reactants and products remain constant over time, but the reactions are still occurring.
• 📝 The equilibrium constant, $K$, expresses the ratio of products to reactants at equilibrium.
• 🔢 For the reaction $aA + bB \rightleftharpoons cC + dD$, the equilibrium constant is: $K = \frac{[C]^c[D]^d}{[A]^a[B]^b}$.
• 🌡️ Le Chatelier's principle states that if a change of condition is applied to a system in equilibrium, the system will shift in a direction that relieves the stress.
• 🔥 Changes in conditions can include changes in concentration, pressure, or temperature.
• 💡 Catalysts speed up both forward and reverse reactions equally, so they do not affect the position of equilibrium, only how quickly it's reached.

Practice Quiz

1. What characterizes a system at chemical equilibrium?
   1. A) The forward reaction has stopped.
   2. B) The reverse reaction has stopped.
   3. C) The rates of the forward and reverse reactions are equal.
   4. D) The concentrations of reactants and products are equal.
2. For the reaction $N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)$, what is the correct equilibrium constant expression?
   1. A) $K = \frac{[N_2][H_2]}{[NH_3]}$
   2. B) $K = \frac{[NH_3]}{[N_2][H_2]}$
   3. C) $K = \frac{[NH_3]^2}{[N_2][H_2]^3}$
   4. D) $K = \frac{[N_2][H_2]^3}{[NH_3]^2}$
3. According to Le Chatelier's principle, what happens if you increase the concentration of a reactant in a system at equilibrium?
   1. A) The equilibrium shifts to favor the reactants.
   2. B) The equilibrium shifts to favor the products.
   3. C) The equilibrium remains unchanged.
   4. D) The reaction stops.
4. Which of the following changes will NOT affect the equilibrium position in a reaction involving gases?
   1. A) Changing the partial pressure of a reactant.
   2. B) Adding an inert gas at constant volume.
   3. C) Changing the temperature.
   4. D) Adding a catalyst.
5. What effect does a catalyst have on a reaction at equilibrium?
   1. A) It shifts the equilibrium towards the products.
   2. B) It shifts the equilibrium towards the reactants.
   3. C) It increases the rate at which equilibrium is reached but does not change the equilibrium position.
   4. D) It changes the equilibrium constant, $K$.
6. Consider the reaction $2SO_2(g) + O_2(g) \rightleftharpoons 2SO_3(g)$. If the pressure is increased, which way will the equilibrium shift?
   1. A) Towards the side with more moles of gas (reactants).
   2. B) Towards the side with fewer moles of gas (products).
   3. C) The equilibrium will not shift.
   4. D) The reaction will stop.
7. For an endothermic reaction, how does increasing the temperature affect the equilibrium constant, $K$?
   1. A) $K$ increases.
   2. B) $K$ decreases.
   3. C) $K$ remains the same.
   4. D) The reaction becomes exothermic.