2..5 grams of platinum will be there at the end of the reaction, because Platinum is the catalyst here.
Catalyst is a substance that can be added to a chemical reaction to increase the rate of reaction without getting itself consumed in the reaction. It just acts as a driving force for the reaction and it itself does not take part in the chemical reaction.
Catalysts basically speeds up a reaction by reducing the activation energy or also by changing the reaction mechanism. Enzymes are proteins that act as catalysts in the biological systems.
In the above given question if 2.5 grams of platinum is added to the reaction vessel then at the end of the reaction 2.5 grams of platinum itself will be remaining because it acts as a catalyst here.
To know more about catalyst
https://brainly.com/question/28813725
#SPJ4