In trial 1, you will use 0.50 g of aluminum, and in trial 2, you will use only 0.25
g. why will you vary the amount of aluminum?

Changing the amount of reactants affects the amount of products produced in a chemical reaction. In a chemical reaction, only the atoms present in the reactants can end up in the products.

In trial one we use 0.50g of aluminium and in trial 2 we use 0.25g while keeping the other factors constant it means that you are changing the mass of reactant to see how it affects your reaction. In this reaction the mass of aluminium is variable that you are changing to see it affects on your reaction.

Or may be in second reaction you need less products so you reduce the amount of reactant.

In a chemical reaction, the number of reactants used and the product produced play a crucial role. Certain experiments are carried out with variable amounts of reactants.

In Trail 1, 0.50 grams of Aluminum is used, whereas, in Trial 2, only 0.25 grams of aluminum is used.

The amount of reactant is varied because the change in the amount of the reactant will affect the number of products produced.

In trial 1, the amount of aluminum used is 0.50 grams. In Trial 2, the amount of aluminum used is 0.25, such that the mass of reactants is changed but the other factors are kept constant.

The change in the mass of the reactants is variable to study the changes occurring in the chemical reaction.

Also, to reduce the number of products produced is required in less amount, thereby the amount of reactant used will be reduced. Trial 2 involved less amount aluminum.

Therefore, the variation in the mass of the reactants is to study the production of the products in a chemical reaction.

To know more about chemical reaction, refer to the following link:

link

allowed for the prediction of the properties of missing elements.