Question 1: Define the term 'catalyst' and explain how transition metals function as catalysts in chemical reactions.

Answer: A catalyst is a substance that increases the rate of a chemical reaction without being consumed. Transition metals function as catalysts by providing an alternative reaction pathway with lower activation energy, often through their variable oxidation states and ability to form temporary bonds with reactants.

Question 1: Describe the general mechanism by which a transition metal catalyst lowers the activation energy for a reaction.

Answer: Transition metal catalysts provide a surface or active sites where reactants can adsorb, forming temporary bonds. This process facilitates the breaking and forming of bonds in reactants, thus lowering the energy barrier (activation energy) needed for the reaction to proceed.

Question 1: The decomposition of hydrogen peroxide (H₂O₂) was studied both in the presence and absence of a manganese dioxide (MnO₂) catalyst. The time taken for 50 mL of oxygen to be released was recorded. Without catalyst: 10 minutes. With MnO₂ catalyst: 2 minutes. Explain how the presence of MnO₂ affects the reaction rate and the likely reason based on catalyst action.

Answer: The presence of MnO₂ significantly increases the reaction rate, reducing the time for oxygen release from 10 to 2 minutes. This is because MnO₂ acts as a catalyst by providing a surface for the reaction, lowering the activation energy, and enabling the reaction to occur more rapidly.

Question 2: If the rate constant (k) for the catalysed reaction is 0.35 min⁻¹ and for the uncatalysed reaction is 0.07 min⁻¹, calculate the factor by which the catalyst increases the reaction rate.

Answer: Factor = rate constant with catalyst / rate constant without catalyst = 0.35 / 0.07 = 5.0

Question 1: Design a simple experiment to test the effect of a transition metal catalyst (such as platinum) on the decomposition of hydrogen peroxide. Mention the variables you would control and safety precautions you would take.

Answer: To test the effect of platinum as a catalyst, I would set up two test tubes with equal volumes of hydrogen peroxide. One would contain a small piece of platinum, and the other would not (control). I would control variables such as temperature, concentration of H₂O₂, and amount of catalyst. Safety precautions include wearing gloves and goggles, conducting the experiment in a well-ventilated area, and handling hydrogen peroxide carefully to avoid spills or skin contact.

Question 1: Identify one industrial process that relies on transition metal catalysts and briefly explain how the catalyst improves the process.

Answer: The Haber process for ammonia synthesis uses an iron catalyst. The catalyst speeds up the reaction between nitrogen and hydrogen gases, making ammonia production more efficient and cost-effective.

Question 2: Explain why catalytic converters in cars contain transition metals and how they benefit the environment.

Answer: Catalytic converters contain transition metals like platinum, palladium, and rhodium to catalyse the conversion of harmful gases (carbon monoxide, nitrogen oxides, hydrocarbons) into less harmful substances (carbon dioxide, nitrogen, water). This reduces pollution and helps protect the environment.

Question 1: Write a short paragraph summarising the importance of transition metals as catalysts in everyday life and industry.

Answer: Transition metals are crucial as catalysts because they can change oxidation states and provide active sites for chemical reactions, thus increasing reaction rates. They are used in many industrial processes such as manufacturing fertilisers, fuels, and cleaning emissions. Their ability to accelerate reactions without being consumed makes them essential for efficient and sustainable chemical processes.