IB Chemistry SL Reactivity 2: How much, how fast and how far? questions

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Question 1

Multiple choiceEasy1 mark

For the reaction shown, Ea=45 kJ mol−1E_\mathrm{a}=45\ \mathrm{kJ\,mol^{-1}} Which proposed collision involves the reactants and has at least this energy?

HH+II2HI
Show answer and explanation

Answer: D. The forward reaction uses H₂ and I₂ as reactants. The activation energy is the minimum energy colliding particles need for a successful collision, so 45 kJ mol⁻¹ meets the stated threshold.

A: uses the correct reactants, but 30 kJ mol⁻¹ is below the activation energy.
B: has sufficient energy but uses HI, which is a product in the forward reaction, instead of I₂.
C: uses the correct reactants, but 44 kJ mol⁻¹ is below the activation energy.
Remember: the collision energy must meet or exceed the activation energy.

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