The presence of a catalyst in a heterogeneous catalyzed reaction significantly affects the rate of the reaction. A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process. In a heterogeneous catalyzed reaction, the catalyst is in a different phase solid, liquid, or gas than the reactants.Catalysts work by providing an alternative reaction pathway with a lower activation energy, which allows more reactant molecules to have sufficient energy to undergo the reaction. This results in an increased rate of reaction.Experimental evidence:One classic example of a heterogeneous catalyzed reaction is the hydrogenation of ethene C2H4 to form ethane C2H6 in the presence of a solid catalyst, such as finely divided platinum or palladium.C2H4 g + H2 g C2H6 g In an experiment to demonstrate the effect of a catalyst on the rate of this reaction, two separate setups can be used. In both setups, a known amount of ethene and hydrogen gas is mixed in a closed container.Setup 1 Control : No catalyst is added to the reaction mixture.Setup 2 Experimental : A known amount of finely divided platinum or palladium catalyst is added to the reaction mixture.The progress of the reaction can be monitored by measuring the decrease in pressure due to the consumption of reactants or the increase in pressure due to the formation of products over time.Results:In the control setup without a catalyst , the reaction rate is observed to be very slow, and it may take a long time for any significant change in pressure to be detected.In the experimental setup with a catalyst , the reaction rate is significantly faster, and a noticeable change in pressure can be observed within a much shorter time.This experimental evidence supports the conclusion that the presence of a catalyst, such as platinum or palladium, significantly increases the rate of the heterogeneous catalyzed reaction between ethene and hydrogen. The catalyst provides an alternative reaction pathway with a lower activation energy, allowing more reactant molecules to undergo the reaction and form products at a faster rate.