Question 1: Define a reversible reaction and describe how it differs from an irreversible reaction.

Answer: A reversible reaction is a chemical reaction where the products can react to form the original reactants, and the process can proceed in both directions. Unlike irreversible reactions, which proceed only in one direction, reversible reactions can reach a state of dynamic equilibrium.

Question 2: Explain what is meant by 'dynamic equilibrium' in the context of reversible reactions.

Answer: Dynamic equilibrium occurs when the forward and backward reactions in a reversible process happen at the same rate, resulting in constant concentrations of reactants and products, though both reactions continue to occur.

Question 1: In a reversible reaction, the rate constant for the forward reaction is 0.05 s⁻¹, and for the backward reaction it is 0.02 s⁻¹. Calculate the ratio of the concentrations of reactants to products at equilibrium using the expression for the equilibrium constant (K).

Answer: K = rate of forward / rate of backward = 0.05 / 0.02 = 2.5. Therefore, the concentration of reactants is 2.5 times that of products at equilibrium.

Question 2: A reversible reaction has an initial concentration of 1.0 mol/L of reactant. After reaching equilibrium, the concentration of reactant is 0.4 mol/L. If the initial concentration of product was zero, calculate the concentration of product at equilibrium.

Answer: Change in reactant concentration = 1.0 - 0.4 = 0.6 mol/L. Since the reaction is reversible and the stoichiometry is 1:1, the concentration of product at equilibrium is 0.6 mol/L.

Question 1: Describe a simple experimental setup to investigate the position of equilibrium in a reversible reaction involving colour change, including safety precautions.

Answer: Use a test tube containing a reversible reaction mixture that shows a colour change, such as iodine and starch. Gently heat the mixture and observe the colour change as the reaction reaches equilibrium. Always wear safety goggles and gloves, and handle hot equipment with tongs to prevent burns.

Question 2: Identify three variables that could affect the position of equilibrium in a reversible reaction and explain their effects.

Answer: Concentration: Increasing concentration of reactants shifts equilibrium to produce more products. Temperature: Raising temperature may favour the endothermic direction. Pressure: For reactions involving gases, increasing pressure shifts equilibrium towards the side with fewer moles of gas.

Question 1: In an experiment, the concentration of reactant A decreases from 1.0 mol/L to 0.4 mol/L over time as it reacts to form product B. The concentration of B increases from 0 mol/L to 0.6 mol/L during the same period. Discuss what this data indicates about the reaction's equilibrium position.

Answer: The data shows that the reaction is approaching equilibrium with a higher concentration of reactant A decreasing and product B increasing. Since the concentrations are not equal, the reaction has not yet reached equilibrium but is moving towards it. The final concentrations suggest the equilibrium favours the formation of B, with the forward reaction being more prominent.

Question 1: Explain how Le Châtelier's Principle applies to the equilibrium shift when pressure is increased in a gaseous reversible reaction with an unequal number of moles of gas on each side. Provide an example scenario.

Answer: Le Châtelier's Principle states that if a change is imposed on a system at equilibrium, the system will adjust to counteract that change. When pressure increases in a gaseous reaction with fewer moles of gas on one side, the equilibrium shifts towards that side to reduce pressure. For example, in the reaction N₂ + 3H₂ ⇌ 2NH₃, increasing pressure favours the formation of ammonia because it reduces the total number of gas molecules, shifting the equilibrium to the right.

Question 1: Describe how reversible reactions are utilised in the Haber process for ammonia production, and explain why controlling temperature and pressure is important.

Answer: The Haber process is a reversible reaction where nitrogen and hydrogen react to form ammonia. Controlling temperature and pressure optimises the yield—high pressure shifts equilibrium towards ammonia, while a moderate temperature balances reaction rate and yield. Excessive temperature speeds up the reaction but reduces yield, so optimal conditions are used to maximise efficiency.

Question 2: Identify a real-world scenario where reversible reactions are critical for environmental or industrial processes and discuss its significance.

Answer: The carbon dioxide–calcium carbonate system in ocean chemistry is a reversible reaction that helps regulate atmospheric CO₂ levels. It is significant for understanding climate change and designing carbon capture technologies.