Is it a synthesis decomposition double displacement or single displacement

Double Displacement

Explanation: The process involves a double displacement reaction where Rubidium ( Rb ) displaces Beryllium ( Be ) and pairs up with Iron ( Fe ). Beryllium then pairs up with Nitrate ( NO3-)

The generic form for this reaction can be expressed in the following form:

AB + CD =>  CB + AD

answer : a model is often used to explain and make things easier to understand when any scientific topic needs to be demonstrated and explained.

as in this case where a scientist wants to use a model to present the results of his detailed scientific investigation. he should do it as it will him to make the audience understand the concept in a much better way. also, it can be changed according to new scientific understandings.