Astack of books are sitting on the table. which force is pulling it down ? a. buoyant force b. pressure force c. gravitational force

There is a gravitational force pulling the stack of books downward. Gravity is always a factor on earth. Keep that in mind when asked these sort of questions. They are made to confuse you. Take your time and you will do just fine.

gravity causes stares to cluster i think so

2fe + 3h2so4 -> fe2(so4)3 + 3h2

it is necessary to balance equations in order to get the proper amount of reactants as well as products in order not to make a miscalculation.

you cannot change the subscripts as that would change the substance itself. for instance, diatomic elements such as h2 only have the subscript two when a gas. another example would be so4, if you were to change the subscript, the element would no longer be sulfate.

we change the coefficients instead as that only changes the number of molecules rather than the substance itself.

hope this !