Combustion reactions involve reacting a substance with oxygen. when compounds containing carbon and hydrogen are combusted, carbon dioxide and water are the products. using the enthalpies of combustion for c4h4 (-2341 kj/mol), c4h8 (-2755 kj/mol), and h2 (-286 kj/mol), calculate δh for this reaction.

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 !

i believe it is c for plato