2X+Y2 + X, Y2 A chemist is studying the reaction between the gaseous chemical species X and Y%, represented by the equation above. Initial rates of reaction are measured at various concentrations of reactants. The results are recorded in the following table. Experiment 1 X] 0.15 0.15 0.30 [Y] 0.10 0.20 0.20 Initial Rate of Appearance of X, Y2 (M/s) 32 64 128 3 A second chemist repeated the three experiments and observed that the reaction rates were considerably greater than those measured by the first chemist even though the concentrations of the reactants and the temperature in the laboratory were the same as they were for the first chemist. Which of the following is the best pairing of a claim about a most likely cause for the greater rates measured by the second chemist and a valid justification for that claim? The pressures of the gases used by the second chemist must have been lower than those used by the first A) chemist, thus the collisions between reacting particles were less frequent than they were in the first chemist's experiments. The pressures of the gases used by the second chemist must have been lower than those used by the first chemist, thus the number of collisions with sufficient energy to cause reaction was lower than it was in the first chemist's experiments. The second chemist must have added a catalyst for the reaction, thus providing a different reaction pathway for the reactant particles to react with an activation energy that was lower than that of the uncatalyzed reaction in the first chemist's experiments. The second chemist must have added a catalyst for the reaction, thus providing energy to reactant particles to increase their rate of reaction compared to their rate of reaction in the first chemist's experiments.