Nitroglycerin, C3H5N3O9, is an unstable compound that decomposes rapidly upon ignition or impact. Below is the thermochemical equation for nitroglycerin: 4 3539 () → 12 2 () + 10 2() + 6 2 () + 13 2 () ∆ = −5678 What mass of nitroglycerin is needed to generate −7285 ?

the answer is b & c i believe : )

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.