Two gaseous samples of the same substance are contained in identical, perfectly insulated vessels. A chemist records the distribution of molecular kinetic energies for each sample on a single graph.
• The x-axis is labeled "kinetic energy, E (kJ mol⁻¹)" and the y-axis is labeled "number of molecules with energy E".
• Curve A has its peak at 55 kJ mol⁻¹ and falls to zero at about 180 kJ mol⁻¹.
• Curve B has a lower maximum height than curve A, its peak is located at 70 kJ mol⁻¹, and it extends to nearly 230 kJ mol⁻¹.
• A vertical dashed line at E = 120 kJ mol⁻¹ represents the minimum energy required for an elementary reaction of the gaseous particles.
Assume that the area under each curve is normalised to 1.0 (i.e., represents the complete population of molecules in the vessel).
(a) Identify which curve corresponds to the sample at the higher absolute temperature and justify your choice by referring to specific features of the curves.
(b) Without performing a numerical calculation, compare the fraction of molecules capable of reacting in the two samples. Explain how this information can be inferred from the graph.
(c) For a reaction that is limited only by the energy criterion (orientation effects are negligible), explain qualitatively how the difference you described in part (b) would influence the initial rate of the reaction in each vessel.