Question

Which event must always occur for a chemical reaction to take place

Answer 1

Answer: Change in chemical composition of reactants is an event which must always occur for a chemical reaction to take place.

Step-by-step explanation:

A chemical reaction is defined as a reaction in which there will always occur change in chemical composition of reactant species.

For example,
`AgNO_(3) + HCl \rightarrow AgCl + HNO_(3)`

Here, chemical composition of both
`AgNO_(3)` and HCl changes which leads to the formation of silver chloride and nitric acid. Hence, it is a chemical reaction.

Therefore, we can conclude that change in chemical composition of reactants is an event which must always occur for a chemical reaction to take place.