A gaseous reaction is carried out in a sealed vessel at 298 K
CHEMISTRY · Single correct · A Level · Chemistry · Kinetics · Kinetics
Problem
A gaseous reaction is carried out in a sealed vessel at 298 K. When finely powdered platinum is dispersed in the mixture, the reaction reaches completion in 45 s. In an otherwise identical trial from which the platinum was omitted, the mixture takes 11 min to reach the same extent of reaction. Which of the following statements best accounts for the observed difference in reaction times?
(a) Platinum increases the frequency of effective collisions by raising the temperature of the system, giving reactants more kinetic energy.
(b) Platinum shifts the equilibrium position toward products, resulting in a faster approach to completion.
(c) Platinum provides an alternative pathway with a lower activation energy, increasing the rate without altering the reaction’s enthalpy change.
(d) Platinum is gradually consumed, so its initial presence accelerates the reaction only until it is depleted.