Consider the following two reactions:Reaction 1: H2 + I2 → 2HI (slow)Reaction 2: NO2 + CO → NO + CO2 (fast)Based on their relative rates, which reaction is likely to have the higher activation energy?

• A. Both reactions have the same activation energy
• B. Reaction 1: H2 + I2 → 2HI
• C. Neither reaction has an activation energy
• D. Reaction 2: NO2 + CO → NO + CO2

Answer: (B)

Verified step by step guidance

1. Understand that the activation energy (Ea) is the minimum energy required for a reaction to proceed and is related to the reaction rate: higher Ea generally means a slower reaction at a given temperature.
2. Note that Reaction 1 (H2 + I2 → 2HI) is described as slow, while Reaction 2 (NO2 + CO → NO + CO2) is fast, indicating that Reaction 1 likely has a higher energy barrier to overcome.
3. Recall the Arrhenius equation: \(k = A e^{-\frac{E_a}{RT}}\), where \(k\) is the rate constant, \(A\) is the frequency factor, \(E_a\) is the activation energy, \(R\) is the gas constant, and \(T\) is temperature; a higher \(E_a\) results in a smaller \(k\), meaning a slower reaction.
4. Since Reaction 1 is slow, its rate constant \(k\) is smaller, implying a larger activation energy \(E_a\) compared to Reaction 2, which is fast and thus has a smaller \(E_a\).
5. Conclude that Reaction 1 has the higher activation energy based on its slower rate relative to Reaction 2.