Factors affecting rate and the Maxwell–Boltzmann distribution
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Flip to reveal answersWhat two conditions make a collision effective?
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All 12 Flashcards — Factors affecting rate and the Maxwell–Boltzmann distribution
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Question
What two conditions make a collision effective?
Answer
Energy **≥ the activation energy (E_{a})** AND the **correct orientation**.
Question
What is activation energy, E_{a}?
Answer
The **minimum** energy a colliding pair of particles must have for a reaction to occur.
Question
Name the five factors that affect reaction rate.
Answer
**Concentration, pressure, surface area, temperature** and a **catalyst**.
Question
How do concentration, pressure and surface area speed up a reaction?
Answer
They put more particles in the reaction space, so collisions are **more frequent** (the energy per collision is unchanged).
Question
Why does raising the temperature increase the rate?
Answer
Particles move faster (collisions **more frequent**) AND the distribution shifts right so a **greater fraction** have energy ≥ E_{a} — the second effect is the main one.
Question
What is a catalyst?
Answer
A substance that speeds up a reaction by providing an **alternative pathway of lower E_{a}**, and is **not used up** itself.
Question
Does a catalyst change ΔH?
Answer
**No** — the reactant and product energy levels are unchanged, so ΔH is the same.
Question
What does the Maxwell-Boltzmann distribution show?
Answer
How the **kinetic energies** of particles are **spread out**; only those to the right of E_{a} can react.
Question
How does a hotter Maxwell-Boltzmann curve look compared with a cooler one?
Answer
**Lower and shifted to the right** (broader/flatter), but with the **same area** underneath.
Question
On a Maxwell-Boltzmann distribution, what does the area to the right of E_{a} represent?
Answer
The **fraction of particles** with enough energy to react (energy ≥ E_{a}).
Question
How does a catalyst change a Maxwell-Boltzmann distribution?
Answer
The curve is **unchanged**; the **E_{a} line moves left**, so a larger fraction lies to the right of it.
Question
Two observations that a solid is acting as a catalyst?
Answer
The reaction goes **faster**, AND the solid is **recovered unchanged** (same mass/nature) at the end.
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How fast? The rate of chemical change
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