.The Carbon Cycle is best defined as the process in which... * Carbon changes from inorganic forms to organic forms and back
Carbon is changed into other elements, including oxygen and hydrogen
Carbon is consumed and regenerated from other elements such as oxygen, hydrogen, and nitrogen
Carbon is continually created from the sun's energy by living organisms

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 !