Rate of reaction and collision theory

Answer

The **change in concentration** of a reactant or product **per unit time**.

Answer

**mol dm⁻³ s⁻¹** — a concentration (mol dm⁻³) divided by a time (s).

Answer

It is the **gradient** (steepness) of the curve — the tangent at a point gives the instantaneous rate.

Answer

The **reactant concentration is highest** at t = 0, so effective collisions are most frequent and the curve is **steepest**.

Answer

**Average** = total change ÷ total time (slope of the **chord**); **instantaneous** = slope of the **tangent** at one moment.

Answer

Particles must **collide** to react, but only **effective** collisions (enough energy + correct orientation) lead to a reaction.

Answer

Energy **≥ the activation energy Eₐ**, AND the particles collide in the **correct orientation**.

Answer

The **minimum energy** that colliding particles must have for a reaction to occur.

Answer

Reactants are **used up**, so their concentration falls and effective collisions become **less frequent**; rate drops to zero when reactants run out.

Answer

Measure the **volume of gas** collected vs time, or the **mass lost** vs time.

Answer

Use a **colorimeter** to measure the **light absorbed** as it changes with time.

Answer

The rate at t = 0 — the **slope of the tangent drawn at the start** of a concentration–time graph (the steepest point).