The chemical equation below shows the burning of magnesium (Mg) with oxygen (O2) to form magnesium oxide (Mgo)
2Mg + O2 → 2Mgo
The molar mass of Oz is 32.0 g/mol. What mass, in grams, of Oz is required to react completely with 4.00 mol of Mg?
2.00
64.0
128
256

64

Explanation:

B

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 !