Rate and collision-theory problem clinic
≈ 50 minRate and collision-theory problem clinic
A rate problem begins by deciding whether the data describe amount, concentration, mass, volume or time to endpoint. Write the rate relationship with correct units, then decide whether the question asks for average rate over an interval or initial rate from a tangent. For explanation marks, name the rate factor and link it to collision theory: concentration changes collision frequency; temperature changes kinetic-energy distribution and collision frequency; surface area changes exposed sites; catalyst lowers activation energy. If a rate constant is supplied in an advanced context, treat it as a proportionality factor at stated temperature, not as a substitute for mechanism.
Work it through
A product concentration rises from 0.10 to 0.34 mol dm⁻³ in 12 s. Average formation rate = (0.34 − 0.10)/12 = 0.020 mol dm⁻³ s⁻¹. If another run has a steeper initial gradient at the same temperature and volume, it has faster initial rate. The graph provides the observation; collision theory explains the possible cause only after the changed variable is identified.
Mastery target
Calculate a rate with units, choose average versus initial rate correctly and write a collision-theory explanation that explicitly links condition to effective collisions.
Which explanation correctly links higher concentration to faster reaction rate?
Name the key chemistry term from Rate and collision-theory problem clinic that best fits the explanation and visual model.
Product concentration rises from 0.10 to 0.34 mol dm⁻³ in 12 s. What is average formation rate in mol dm⁻³ s⁻¹?
Which statement corrects a common misunderstanding in Rate and collision-theory problem clinic?