In the reaction 3h2+ n2 --> 2 nh3, what coefficient should be placed in front of n2 to balance the reaction?

a. 1
b. 2
c. 3
d. no coefficient is needed

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.