gen-briefly-explain-reaction-rate-and-rate-laws-and-one-common-m-1607

Briefly explain reaction rate and rate laws and one common misconception about it.

# Reaction Rate and Rate Laws ## Reaction Rate **Reaction rate** measures how fast reactants are consumed or products are formed over time. It's typically expressed as the change in concentration per unit time (e.g., mol/L·s). ## Rate Laws A **rate law** is an equation that relates the reaction rate to reactant concentrations: **Rate = k[A]^m[B]^n** Where: - k = rate constant - [A], [B] = concentrations of reactants - m, n = reaction orders (determined experimentally) The rate law shows which reactants affect the speed and by how much. ## Common Misconception **Misconception:** *The exponents in the rate law match the stoichiometric coefficients in the balanced equation.* **Reality:** Rate law exponents must be determined **experimentally**—they cannot be predicted from the balanced equation alone. For example: - Equation: 2NO₂ + F₂ → 2NO₂F - Rate law: Rate = k[NO₂][F₂] (NOT k[NO₂]²[F₂]) The stoichiometric coefficients only match rate law exponents for **elementary reactions** (single-step mechanisms), but most reactions occur through multiple steps.