Question 1: Activation energy is the minimum amount of energy required for a chemical reaction to occur. It is represented as the energy barrier that reactants must overcome to form products. Understanding activation energy helps explain why some reactions happen quickly and others slowly.

Answer: Activation energy is the minimum energy needed for reactants to undergo a chemical reaction, overcoming the energy barrier.

Question 1: Define activation energy in your own words.

Answer: Activation energy is the energy required to start a chemical reaction by allowing reactants to reach the transition state.

Question 2: Explain how activation energy influences the rate of a chemical reaction.

Answer: Higher activation energy means a slower reaction rate because fewer molecules have enough energy to overcome the barrier. Lower activation energy results in a faster reaction.

Question 1: A reaction has an activation energy of 50 kJ/mol. If the temperature is increased from 25°C to 35°C, how does this affect the number of molecules able to react? (Hint: Use the Arrhenius equation approximation).

Answer: The ratio of molecules with enough energy at the two temperatures is approximately e^{(-Ea/RT1)} / e^{(-Ea/RT2)}. Using R=8.314 J/mol·K, T1=298K, T2=308K, Ea=50,000 J/mol, the calculation shows an increase in reaction rate by about 25%.

Question 2: Calculate the activation energy if the rate constant at 25°C is 0.02 s⁻¹ and at 35°C is 0.05 s⁻¹. Use the Arrhenius equation: k = A * e^(-Ea/RT).

Answer: Ea = (R * T1 * T2 / (T2 - T1)) * ln(k2 / k1). Substituting the values, Ea ≈ 35 kJ/mol.

Question 1: Describe an experiment to determine the activation energy of a reaction. Include the variables involved and safety precautions.

Answer: An experiment involves measuring reaction rates at different temperatures, typically by recording the time taken for a reactant to be consumed. Variables include temperature (independent), reaction time (dependent), and concentration (controlled). Safety precautions include wearing goggles, gloves, and handling chemicals carefully to avoid spills or burns.

Question 2: Identify three variables that can affect the measurement of activation energy in an experiment and suggest ways to control them.

Answer: Variables include temperature, reactant concentration, and catalyst presence. To control them, maintain constant temperature using a water bath, keep reactant concentrations consistent, and avoid adding catalysts unless studying their effect.

Question 1: A student observes that increasing temperature from 20°C to 30°C doubles the rate of a reaction. What does this suggest about the activation energy? Explain briefly.

Answer: This suggests the activation energy is relatively low because a small temperature increase significantly increases the reaction rate, indicating molecules more easily overcome the energy barrier.

Question 1: How do catalysts in industrial processes affect activation energy and reaction rates? Provide an example.

Answer: Catalysts lower the activation energy, allowing reactions to occur more quickly at lower temperatures. For example, the use of catalytic converters in cars reduces harmful emissions by speeding up the conversion of pollutants.

Question 2: Explain why cooking food at higher temperatures decreases cooking time. Relate this to activation energy.

Answer: Higher temperatures provide more molecules with enough energy to overcome the activation energy barrier, increasing the reaction rate and reducing cooking time.