The three elements are Zinc , Aluminium and Magnesium.

THE ELEMENTS IN DECREASING ORDER OF REACTIVITY IS

Magnesium > Aluminium > Zinc

Arranging Elements in Decreasing Order of Reactivity

To arrange the elements in decreasing order of reactivity, we need to analyze the given equations and determine the order in which the elements react with each other.

1. Reactivity of A and B:

In the first equation, A2O3 reacts with 2B to give B2O3 and 2A. This indicates that A is more reactive than B because it is able to oxidize B to form B2O3.

2. Reactivity of B and C:

In the second equation, 3CSo4 reacts with 2B to give B2(So4)3 and 3C. This indicates that B is more reactive than C because it is able to oxidize C to form B2(So4)3.

3. Reactivity of A and C:

In the third equation, 3Co reacts with 2A to give A2O3 and 3C. This indicates that A is more reactive than C because it is able to oxidize C to form A2O3.

Therefore, the order of decreasing reactivity is: A > B > C.

Explanation:

Reactivity is a measure of how easily an element can undergo a chemical reaction with another element or compound. In the given equations, we see that each element is reacting with another element or compound to form a new product. The reactants on the left side of the equation are being transformed into products on the right side of the equation.

In the first equation, A2O3 is reacting with 2B to give B2O3 and 2A. This indicates that A is more reactive than B because it is able to oxidize B to form B2O3. In other words, A is able to take oxygen away from B and form a new compound.

Similarly, in the second equation, 3CSo4 is reacting with 2B to give B2(So4)3 and 3C. This indicates that B is more reactive than C because it is able to oxidize C to form B2(So4)3.

In the third equation, 3Co is reacting with 2A to give A2O3 and 3C. This indicates that A is more reactive than C because it is able to oxidize C to form A2O3.

Thus, we can conclude that A is the most reactive element, followed by B, and then C.