The reaction between hydrogen iodide (HI) and oxygen (O₂) occurs in two steps:
HI + O2 → HIO2 (fast)
HIO2 + HI → H2O + I2 (slow)
Identify the molecularity of each elementary step.
Write the rate law for the overall reaction based on the rate-determining step.
Justify why the second step determines the rate of the overall reaction.
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Consider the reaction between carbon monoxide (CO) and chlorine (Cl2):
CO (g) + Cl2 (g) → COCl2 (g)
Explain why increasing the temperature increases the rate of reaction.
Describe how the orientation of CO and Cl2 molecules during collision affects the reaction rate.
Define what is meant by an “effective collision.”
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The graph below shows the Maxwell-Boltzmann distribution curve for a gas at 300 K.
Sketch the distribution curve for the same gas at 350 K on the same graph. Ensure your curve shows the shift in the fraction of particles with energy ≥ Ea.
Explain how the shift in the fraction of particles with energy ≥ Ea affects the reaction rate at 350 K compared to 300 K.
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The reaction between methane (CH4) and chlorine (Cl) is initiated by light:
CH4 + Cl2 → CH3Cl + HCl
Explain the role of light in initiating the reaction.
Draw a reaction energy profile for the exothermic reaction described in part (a), labelling the activation energy and ΔH.
Explain what a transition state is in a reaction.
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