Question 1: A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process. Catalysts work by providing an alternative reaction pathway with a lower activation energy. Explain how a catalyst affects the rate of a reaction.

Answer: A catalyst lowers the activation energy, allowing more particles to have sufficient energy to react, thereby increasing the reaction rate without being consumed.

Question 1: Describe the mechanism by which a catalyst speeds up a chemical reaction.

Answer: A catalyst provides an alternative pathway with a lower activation energy, increasing the number of particles that can react at a given temperature, thus speeding up the reaction.

Question 2: Name two common catalysts used in industry and the reactions they catalyse.

Answer: Iron in the Haber process for ammonia synthesis; Platinum in catalytic converters for reducing vehicle emissions.

Question 1: A reaction normally takes 60 minutes without a catalyst. When a catalyst is used, the reaction takes 15 minutes. Calculate the percentage increase in the reaction rate due to the catalyst.

Answer: Percentage increase in rate = (Time without catalyst / Time with catalyst) × 100 = (60 / 15) × 100 = 400%

Question 2: The activation energy for a reaction is 80 kJ/mol without a catalyst. With a catalyst, it drops to 40 kJ/mol. Using the Arrhenius equation, estimate the ratio of reaction rates at 25°C (298 K) with and without the catalyst. (Use R = 8.314 J/mol·K)

Answer: Rate ratio ≈ e^{(Ea / R) * (1 / T1 - 1 / T2)} = e^{(80000 / 8.314) * (1/298 - 1/298)} = 1 (since same temperature, but with different Ea, calculation involves exponential of Ea difference): Rate ratio ≈ e^{( (80000 - 40000) / 8.314) * (1/298)} ≈ e^{(40000 / 8.314) * (1/298)} ≈ e^{(4810) * 0.00336} ≈ e^{16.16} ≈ 1,000,000. Therefore, the rate with the lower activation energy is approximately a million times faster at 25°C.

Question 1: Design a simple experiment to test the effect of a catalyst on the rate of decomposition of hydrogen peroxide. List the variables you would control and safety precautions you would take.

Answer: The experiment involves adding a fixed amount of hydrogen peroxide to two test tubes, one with a catalyst (e.g., manganese dioxide) and one without. Variables to control include temperature, concentration, and volume of hydrogen peroxide. Safety precautions include wearing goggles, gloves, and working in a well-ventilated area to handle hydrogen peroxide, which is a strong oxidiser.

Question 2: Identify three factors that can affect the efficiency of a catalyst in an industrial process.

Answer: Temperature, surface area of the catalyst, and presence of impurities or poisons that can deactivate the catalyst.

Question 1: A catalytic converter uses platinum to reduce harmful emissions from vehicles. Explain how the catalyst works and why platinum is used.

Answer: The platinum in catalytic converters catalyses the conversion of harmful gases like carbon monoxide and nitrogen oxides into less harmful substances such as carbon dioxide and nitrogen. Platinum is used because it is a noble metal that is highly effective as a catalyst, resistant to corrosion, and can operate at high temperatures typical of exhaust gases.

Question 2: In the industrial synthesis of ammonia via the Haber process, iron is used as a catalyst. Discuss the importance of catalysts in chemical manufacturing and their economic impact.

Answer: Catalysts like iron in the Haber process are vital because they increase reaction rates and yields, making production more efficient and cost-effective. This reduces energy consumption and raw material costs, leading to lower prices for chemicals and supporting large-scale industrial manufacturing. Catalysts also enable reactions to occur under milder conditions, decreasing environmental impact.