A test tube contains a pure colourless gas. It is either oxygen, carbon dioxide, hydrogen or nitrogen. When a burning splint is put into the gas it just goes out. you are allowed only one more test to identify the gas. Say what the test is, and how you would reach your answer.

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 !