Quiz on Chemical Equilibrium for 10th Grade Chemistry Students

📚 Quick Study Guide

• ⚖️ Chemical equilibrium is a 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 happening!
• 🌡️ Changes in temperature, pressure, or concentration can shift the equilibrium position. This is described by Le Chatelier's principle.
• 🔑 Le Chatelier's Principle: If a change of condition is applied to a system in equilibrium, the system will shift in a direction that relieves the stress.
• 📈 Effect of Concentration: Adding more reactants shifts the equilibrium to the products side; adding more products shifts it to the reactants side.
• 🔥 Effect of Temperature: For exothermic reactions (heat is released), increasing temperature shifts the equilibrium to the reactants side. For endothermic reactions (heat is absorbed), increasing temperature shifts the equilibrium to the products side.
• 💨 Effect of Pressure (for gases): Increasing pressure favors the side with fewer moles of gas.
• 📝 The equilibrium constant, $K_c$, is the ratio of product concentrations to reactant concentrations at equilibrium: $K_c = \frac{[Products]}{[Reactants]}$

🧪 Practice Quiz

1. Which of the following describes chemical equilibrium?
   1. A) The point where all reactants are converted to products.
   2. B) The point where the rate of the forward reaction equals the rate of the reverse reaction.
   3. C) The point where the reaction stops completely.
   4. D) The point where only products are present.


2. According to Le Chatelier's principle, what happens when you increase the concentration of reactants in a system at equilibrium?
   1. A) The equilibrium shifts towards the reactants.
   2. B) The equilibrium shifts towards the products.
   3. C) There is no change in the equilibrium.
   4. D) The reaction stops.


3. For an exothermic reaction, what happens to the equilibrium when you increase the temperature?
   1. A) The equilibrium shifts towards the reactants.
   2. B) The equilibrium shifts towards the products.
   3. C) There is no change in the equilibrium.
   4. D) The reaction speeds up.


4. Which of the following changes will NOT affect the equilibrium position in a reaction involving only liquids and solids?
   1. A) Change in concentration.
   2. B) Change in pressure.
   3. C) Change in temperature.
   4. D) Addition of a catalyst.


5. Consider the following reaction: $N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)$. If the pressure is increased, what will happen to the equilibrium?
   1. A) Shift to the side with more moles of gas ($N_2$ and $H_2$).
   2. B) Shift to the side with fewer moles of gas ($NH_3$).
   3. C) No change.
   4. D) The reaction will stop.


6. What does a large value of the equilibrium constant, $K_c$, indicate?
   1. A) The reaction favors the reactants.
   2. B) The reaction favors the products.
   3. C) The reaction is very slow.
   4. D) The reaction is at equilibrium.


7. In the reaction $A + B \rightleftharpoons C + D$, if $[A] = 2M$, $[B] = 1M$, $[C] = 4M$, and $[D] = 2M$ at equilibrium, what is the value of $K_c$?
   1. A) 1
   2. B) 2
   3. C) 4
   4. D) 8