CHEMISTRY · Multi-part · AP · Chemistry · Properties of Substances and Mixtures · Properties of Substances and Mixtures
Problem
For a gaseous reactant at 310 K, the speeds of 5.0 × 10³ representative molecules were recorded and sorted into the intervals shown below. (The distribution is assumed to be proportional to that of the entire sample.)
Speed interval (m s⁻¹) | Number of molecules
0 – 200 | 780
200 – 400 | 1 160
400 – 600 | 1 150
600 – 800 | 900
800 – 1 000 | 600
1 000 – 1 200 | 310
1 200 – 1 400 | 80
> 1 400 | 20
A collision must occur at or above a speed of 1 050 m s⁻¹ for the reactants to surmount the activation energy barrier.
(a) Calculate the fraction of the recorded molecules that have speeds equal to or greater than 1 050 m s⁻¹.
(b) Express this fraction as a percentage of all collisions at 310 K that are expected to be energetic enough to react.
(c) Explain why the calculated percentage is only an approximation of the true fraction of successful collisions in the bulk gas sample.