A chemist has some propene, H2C= CHCH3, in a compressed gas tank to convert to propane, H3CCH2CH3. The first thought is to combine the gas from the propene tank with that from a tank of a compressed hydrogen gas, H2. However, when this is tried nothing happens. The chemist finds some powdered palladium mixed in with inert charcoal in the chemical supply cabinet. Under conditions controlled for temperature and pressure, the chemist places the palladium into the flowpath from the hydrogen and propene tanks. As the mixuture of propene and hydrogen flows past the palladium, a reaction occurs so that when the gas reaches the temperature controlled receiving tanks, it is propane gas. After all the propene has been converted to propane, the curious chemist pours the palladium-charcoal mixture into a crucible. After analyzing the palladium, the chemist confirms that the chemical state has not changed.
What word best describes the role that the palladium plays in the reaction between propene and hydrogen?
a) It is a catalyst.
b) It is an activation energy barrier.
c) It is a solvent.
d) It is a reagent.